--- a/layout/style/test/moz.build
+++ b/layout/style/test/moz.build
@@ -110,16 +110,21 @@ TEST_HARNESS_FILES.testing.mochitest.tes
     '/layout/reftests/fonts/Ahem.ttf',
     '/layout/reftests/svg/as-image/lime100x100.svg',
     '/layout/reftests/svg/as-image/svg-image-visited-1-helper.svg',
     '/layout/reftests/svg/as-image/svg-image-visited-2-helper.svg',
     '/layout/reftests/svg/pseudo-classes-02-ref.svg',
     '/layout/reftests/svg/pseudo-classes-02.svg',
 ]
 
+if CONFIG['MOZ_STYLO']:
+    TEST_HARNESS_FILES.testing.mochitest.tests.layout.style.test += [
+        'stylo-failures.md',
+    ]
+
 DEFINES['MOZILLA_INTERNAL_API'] = True
 if CONFIG['MOZ_ENABLE_MASK_AS_SHORTHAND']:
    HOST_DEFINES['MOZ_ENABLE_MASK_AS_SHORTHAND'] = True
 
 if CONFIG['COMPILE_ENVIRONMENT']:
     GENERATED_FILES += ['css_properties.js']
     GENERATED_FILES['css_properties.js'].script = 'gen-css-properties.py'
     GENERATED_FILES['css_properties.js'].inputs = [

new file mode 100644
--- /dev/null
+++ b/layout/style/test/stylo-failures.md
@@ -0,0 +1,641 @@
+This file describes test failures we currently have for stylo.
+
+Failure patterns are described in the following format:
+* test_name.html [number]
+* test_name.html `pattern` [number]
+* test_name.html: description [number]
+* test_name.html `pattern`: description [number]
+* test_name.html asserts [number]
+* test_name.html asserts: description [number]
+
+In which
+* test_name.html is the name of the test. It could be "..." which means
+  the same name as the previous failure pattern.
+* description is a comment for the supposed reason of the failure.
+* [number] is the expected count of the failure, which can be a "*" meaning
+  any positive number.
+* `pattern` is a substring of the failure message. If there are multiple items
+  for the same test file, a failure is captured by the first matched pattern.
+  For example, if there is a failure with message "foo bar", and there is a
+  pattern `foo` followed by a pattern `bar`, this failure would be counted in
+  the pattern `foo`.
+* "asserts" means it is for assertion. Number of assertions of a same test is
+  accumulated, unlike `pattern`. And number of assertions cannot be "*".
+
+Any line which doesn't follow the format above would be ignored like comment.
+
+## Failures
+
+* Media query support:
+  * test_acid3_test46.html: @media support [13]
+  * test_bug1089417.html [1] **disabled**
+  * test_bug418986-2.html: matchMedia support [3]
+  * test_bug453896_deck.html: <style media> support [8]
+  * test_media_queries.html [1]
+  * test_media_queries_dynamic.html [17]
+  * test_media_queries_dynamic_xbl.html [2]
+  * test_webkit_device_pixel_ratio.html: -webkit-device-pixel-ratio [3]
+* test_all_shorthand.html: all shorthand servo/servo#15055 [*]
+* Animation support:
+  * test_animations.html [277]
+  * test_animations_async_tests.html [3]
+  * test_animations_dynamic_changes.html [1]
+  * test_bug716226.html [1]
+  * test_flexbox_flex_grow_and_shrink.html [16]
+  * OMTA
+    * test_animations_effect_timing_duration.html [1]
+    * test_animations_effect_timing_enddelay.html [1]
+    * test_animations_effect_timing_iterations.html [1]
+    * test_animations_iterationstart.html [1]
+    * test_animations_omta.html [1]
+    * test_animations_omta_start.html [1]
+    * test_animations_pausing.html [1]
+    * test_animations_playbackrate.html [1]
+  * Events:
+    * test_animations_event_handler_attribute.html [10]
+    * test_animations_event_order.html [11]
+  * SMIL Animation
+    * test_restyles_in_smil_animation.html [2]
+  * Property parsing and computation:
+    * test_inherit_computation.html `animation` [6]
+    * test_initial_computation.html `animation` [12]
+    * test_property_syntax_errors.html `animation` [464]
+    * test_value_storage.html `animation` [1078]
+* test_any_dynamic.html: -moz-any pseudo class [2]
+* CSSOM support:
+  * @namespace ##easy##
+    * test_at_rule_parse_serialize.html [1]
+    * test_bug765590.html [1]
+    * test_font_face_parser.html `@namespace` [1]
+  * @import
+    * test_bug221428.html [1]
+  * @media
+    * test_condition_text_assignment.html [1]
+    * test_css_eof_handling.html [1]
+    * test_group_insertRule.html [16]
+    * test_rules_out_of_sheets.html [1]
+  * @keyframes
+    * test_keyframes_rules.html [1]
+  * @support
+    * test_supports_rules.html [1]
+* test_box_size_keywords.html: moz-prefixed intrinsic size keyword value [64]
+* test_bug160403.html: servo/servo#15004 [2]
+* test_bug229915.html: sibling selector with dynamic change bug 1330885 [5]
+* test_bug357614.html: case-insensitivity for old attrs in attr selector servo/servo#15006 [2]
+* mapped attribute not supported
+  * test_bug363146.html [2]
+  * test_bug389464.html: also font-size computation [1]
+  * test_html_attribute_computed_values.html: also list-style-type [9]
+* test_bug387615.html: getComputedStyle value not updated bug 1331294 ##important## (when that gets fixed, servo/servo#15006) [1]
+* test_bug397427.html: @import issue bug 1331291 and CSSOM support of @import [2]
+* console support:
+  * test_bug413958.html `monitorConsole` [3]
+  * test_parser_diagnostics_unprintables.html [550]
+* test_bug511909.html: @-moz-document and @media support [4]
+* Style change from DOM API bug 1331301
+  * test_bug534804.html [90]
+  * test_bug73586.html [76]
+* Transition support:
+  * test_bug621351.html [4]
+  * test_compute_data_with_start_struct.html `transition` [8]
+  * test_inherit_computation.html `transition` [30]
+  * test_initial_computation.html `transition` [60]
+  * test_transitions.html [65]
+  * test_transitions_and_reframes.html [16]
+  * test_transitions_and_restyles.html [3]
+  * test_transitions_computed_value_combinations.html [553]
+  * test_transitions_computed_values.html [10]
+  * test_transitions_dynamic_changes.html [10]
+  * test_transitions_step_functions.html [24]
+  * test_value_storage.html `transition` [635]
+* test_bug798843_pref.html: conditional opentype svg support [7]
+* test_computed_style.html `gradient`: -moz-prefixed radient value [9]
+* url value in style attribute bug 1310886
+  * test_computed_style.html `url` [18]
+  * test_parse_url.html [66]
+  * test_value_storage.html `url` [850]
+  * test_shorthand_property_getters.html `background shorthand` [1]
+  * ... `url` [3]
+* test_computed_style.html `mask`: setting mask shorthand resets subproperties to non-initial value bug 1331516 [11]
+* auto value for min-{width,height} servo/servo#15045
+  * test_computed_style_min_size_auto.html [14]
+  * test_compute_data_with_start_struct.html `height` [4]
+  * ... `min-width` [2]
+  * ... ` width` [1]
+  * test_value_storage.html `'auto' on 'min-` [4]
+* test_compute_data_with_start_struct.html `timing-function`: incorrectly computing keywords to bezier function servo/servo#15086 [2]
+* test_condition_text.html: @-moz-document, CSSOM support of @media, @support [2]
+* @counter-style support:
+  * test_counter_descriptor_storage.html [1]
+  * test_counter_style.html [1]
+  * test_rule_insertion.html `@counter-style` [4]
+  * test_value_storage.html `symbols(` [30]
+  * ... `list-style-type` [74]
+  * ... `'list-style'` [30]
+* test_default_computed_style.html: support of getDefaultComputedStyle [1]
+* @font-face support bug 1290237
+  * test_descriptor_storage.html [1]
+  * test_descriptor_syntax_errors.html [1]
+  * test_font_face_parser.html `@font-face` [447]
+  * test_redundant_font_download.html [3] **disabled**
+* @namespace support:
+  * test_namespace_rule.html [17]
+* test_dont_use_document_colors.html: support of disabling document color [21]
+* test_exposed_prop_accessors.html: mainly various unsupported properties [*]
+* test_extra_inherit_initial.html: CSS-wide keywords are accepted as part of value servo/servo#15054 [946]
+* flex-basis glue not implemented bug 1331529
+  * test_flexbox_flex_shorthand.html `flex-basis` [28]
+  * test_flexbox_layout.html [355]
+  * test_compute_data_with_start_struct.html `flex-basis` [2]
+  * test_inherit_computation.html `flex-basis` [4]
+  * test_initial_computation.html `flex-basis` [8]
+* test_font_feature_values_parsing.html: @font-feature-values support [107]
+* Grid support:
+  * test_grid_computed_values.html [4]
+  * test_grid_container_shorthands.html [65]
+  * test_grid_item_shorthands.html [23]
+  * test_grid_shorthand_serialization.html [28]
+  * test_compute_data_with_start_struct.html `grid-` [*]
+  * test_inherit_computation.html `grid` [*]
+  * test_inherit_storage.html `'grid` [*]
+  * ... `"grid` [*]
+  * test_initial_computation.html `grid` [*]
+  * test_initial_storage.html `grid` [*]
+  * test_property_syntax_errors.html `grid`: actually there are issues with this [*]
+  * test_value_storage.html `'grid` [*]
+* test_hover_quirk.html: hover quirks [6]
+* url value from decl setter bug 1330503
+  * test_compute_data_with_start_struct.html `-moz-binding` [2]
+  * ... `border-image-source` [2]
+  * ... `background-image` [2]
+  * ... `clip-path` [2]
+  * ... `filter` [2]
+  * ... `list-style-image` [2]
+  * ... `mask-image` [2]
+  * test_inherit_computation.html `-moz-binding` [2]
+  * ... `border-image` [8]
+  * ... `background-image` [2]
+  * ... `clip-path` [2]
+  * ... `filter` [4]
+  * ... `list-style-image` [4]
+  * ... `mask-image` [4]
+  * test_initial_computation.html `-moz-binding` [4]
+  * ... `border-image` [16]
+  * ... `background-image` [4]
+  * ... `clip-path` [4]
+  * ... `filter'` [8]
+  * ... `list-style-image` [2]
+  * ... `mask-image` [8]
+* Unimplemented prefixed properties:
+  * -moz-border-*-colors
+    * test_compute_data_with_start_struct.html `-colors` [8]
+    * test_inherit_computation.html `-colors` [8]
+    * test_inherit_storage.html `-colors` [12]
+    * test_initial_computation.html `-colors` [16]
+    * test_initial_storage.html `-colors` [24]
+    * test_value_storage.html `-colors` [96]
+    * test_shorthand_property_getters.html `-colors` [1]
+  * -moz-box-{direction,ordinal-group,orient,pack}
+    * test_compute_data_with_start_struct.html `-moz-box-` [8]
+    * test_inherit_computation.html `-box-` [16]
+    * test_inherit_storage.html `-box-` [20]
+    * test_initial_computation.html `-box-` [32]
+    * test_initial_storage.html `-box-` [40]
+    * test_value_storage.html `-box-` [172]
+  * -moz-force-broken-image-icon
+    * test_compute_data_with_start_struct.html `-moz-force-broken-image-icon` [2]
+    * test_inherit_computation.html `-moz-force-broken-image-icon` [2]
+    * test_inherit_storage.html `-moz-force-broken-image-icon` [2]
+    * test_initial_computation.html `-moz-force-broken-image-icon` [4]
+    * test_initial_storage.html `-moz-force-broken-image-icon` [4]
+    * test_value_storage.html `-moz-force-broken-image-icon` [4]
+  * -{moz,webkit}-text-size-adjust
+    * test_compute_data_with_start_struct.html `-text-size-adjust` [2]
+    * test_inherit_computation.html `-text-size-adjust` [8]
+    * test_inherit_storage.html `-text-size-adjust` [10]
+    * test_initial_computation.html `-text-size-adjust` [4]
+    * test_initial_storage.html `-text-size-adjust` [5]
+    * test_value_storage.html `-text-size-adjust` [12]
+  * -moz-transform: need different parsing rules
+    * test_inherit_computation.html `-moz-transform`: need different parsing rules [2]
+    * test_inherit_storage.html `transform`: for -moz-transform [3]
+    * test_initial_computation.html `-moz-transform`: need different parsing rules [4]
+    * test_initial_storage.html `transform`: for -moz-transform [6]
+    * test_value_storage.html `-moz-transform`: need different parsing rules [280]
+  * test_variables.html `var(--var6)`: -x-system-font [1]
+* Unimplemented CSS properties:
+  * will-change longhand property
+    * test_change_hint_optimizations.html [1]
+    * test_compute_data_with_start_struct.html `will-change` [2]
+    * test_inherit_computation.html `will-change` [2]
+    * test_inherit_storage.html `will-change` [2]
+    * test_initial_computation.html `will-change` [4]
+    * test_initial_storage.html `will-change` [4]
+    * test_value_storage.html `will-change` [18]
+  * contain longhand property
+    * test_contain_formatting_context.html [1]
+    * test_compute_data_with_start_struct.html `contain` [2]
+    * test_inherit_computation.html `contain` [2]
+    * test_inherit_storage.html `contain` [2]
+    * test_initial_computation.html `contain` [4]
+    * test_initial_storage.html `contain` [4]
+    * test_value_storage.html `'contain'` [30]
+  * flexbox / grid position properties servo/servo#15001
+    * test_align_justify_computed_values.html [96]
+    * test_compute_data_with_start_struct.html `align-` [4]
+    * ... `justify-` [6]
+    * test_inherit_computation.html `align-` [8]
+    * ... `justify-` [8]
+    * test_inherit_storage.html `align-` [8]
+    * ... `justify-` [12]
+    * test_initial_computation.html `align-` [16]
+    * ... `justify-` [16]
+    * test_initial_storage.html `align-` [16]
+    * ... `justify-` [24]
+    * test_value_storage.html `align-` [198]
+    * ... `justify-` [229]
+  * place-{content,items,self} shorthands
+    * test_align_shorthand_serialization.html [8]
+    * test_inherit_computation.html `place-` [6]
+    * test_inherit_storage.html `place-` [6]
+    * test_initial_computation.html `place-` [12]
+    * test_initial_storage.html `place-` [12]
+    * test_value_storage.html `place-` [66]
+  * caret-color servo/servo#15309
+    * test_compute_data_with_start_struct.html `caret-color` [2]
+    * test_inherit_computation.html `caret-color` [4]
+    * test_inherit_storage.html `caret-color` [4]
+    * test_initial_computation.html `caret-color` [2]
+    * test_initial_storage.html `caret-color` [2]
+    * test_value_storage.html `caret-color` [16]
+  * font-variant-{alternates,east-asian,ligatures,numeric} properties
+    * test_compute_data_with_start_struct.html `font-variant` [8]
+    * test_inherit_computation.html `font-variant` [20]
+    * test_inherit_storage.html `font-variant` [36]
+    * test_initial_computation.html `font-variant` [10]
+    * test_initial_storage.html `font-variant` [18]
+    * test_value_storage.html `font-variant` [332]
+  * initial-letter property
+    * test_compute_data_with_start_struct.html `initial-letter` [2]
+    * test_inherit_computation.html `initial-letter` [2]
+    * test_inherit_storage.html `initial-letter` [2]
+    * test_initial_computation.html `initial-letter` [4]
+    * test_initial_storage.html `initial-letter` [4]
+    * test_value_storage.html `initial-letter` [10]
+  * shape-outside property
+    * test_compute_data_with_start_struct.html `shape-outside` [2]
+    * test_inherit_computation.html `shape-outside` [2]
+    * test_inherit_storage.html `shape-outside` [2]
+    * test_initial_computation.html `shape-outside` [4]
+    * test_initial_storage.html `shape-outside` [4]
+    * test_value_storage.html `shape-outside` [121]
+  * touch-action property
+    * test_compute_data_with_start_struct.html `touch-action` [2]
+    * test_inherit_computation.html `touch-action` [2]
+    * test_inherit_storage.html `touch-action` [2]
+    * test_initial_computation.html `touch-action` [4]
+    * test_initial_storage.html `touch-action` [4]
+    * test_value_storage.html `touch-action` [14]
+* Unimplemented SVG properties:
+  * fill property
+    * test_compute_data_with_start_struct.html `fill` [2]
+    * test_inherit_computation.html `fill` [4]
+    * test_inherit_storage.html `fill` [4]
+    * test_initial_computation.html `fill` [2]
+    * test_initial_storage.html `fill` [2]
+    * test_value_storage.html `on 'fill'` [25]
+  * marker-{start,mid,end} properties
+    * test_compute_data_with_start_struct.html `marker-` [6]
+    * test_inherit_computation.html `marker` [16]
+    * test_inherit_storage.html `marker` [22]
+    * test_initial_computation.html `marker` [8]
+    * test_initial_storage.html `marker` [11]
+    * test_value_storage.html `on 'marker` [15]
+  * paint-order property
+    * test_compute_data_with_start_struct.html `paint-order` [2]
+    * test_inherit_computation.html `paint-order` [4]
+    * test_inherit_storage.html `paint-order` [4]
+    * test_initial_computation.html `paint-order` [2]
+    * test_initial_storage.html `paint-order` [2]
+    * test_value_storage.html `on 'paint-order` [10]
+  * stroke properties
+    * test_compute_data_with_start_struct.html `stroke` [8]
+    * test_inherit_computation.html `'stroke` [16]
+    * test_inherit_storage.html `'stroke` [8]
+    * ... `"stroke` [8]
+    * test_initial_computation.html `'stroke` [8]
+    * test_initial_storage.html `'stroke` [4]
+    * ... `"stroke` [4]
+    * test_value_storage.html `on 'stroke` [71]
+* Properties implemented but not in geckolib:
+  * counter-reset property:
+    * test_bug829816.html [8]
+    * test_compute_data_with_start_struct.html `counter-reset` [2]
+    * test_inherit_computation.html `counter-reset` [2]
+    * test_inherit_storage.html `counter-reset` [2]
+    * test_initial_computation.html `counter-reset` [4]
+    * test_initial_storage.html `counter-reset` [4]
+    * test_value_storage.html `counter-reset` [30]
+  * counter-increment property:
+    * test_parse_ident.html [133]
+    * test_compute_data_with_start_struct.html `counter-increment` [2]
+    * test_inherit_computation.html `counter-increment` [2]
+    * test_inherit_storage.html `counter-increment` [2]
+    * test_initial_computation.html `counter-increment` [4]
+    * test_initial_storage.html `counter-increment` [4]
+    * test_value_storage.html `counter-increment` [30]
+  * clip property
+    * test_compute_data_with_start_struct.html `clip` [2]
+    * test_inherit_computation.html `clip` [2]
+    * test_inherit_storage.html `clip` [2]
+    * test_initial_computation.html `'clip'` [4]
+    * test_initial_storage.html `clip` [4]
+    * test_value_storage.html `on 'clip'` [12]
+  * font-feature-settings property
+    * test_compute_data_with_start_struct.html `font-feature-settings` [2]
+    * test_inherit_computation.html `font-feature-settings` [8]
+    * test_inherit_storage.html `font-feature-settings` [12]
+    * test_initial_computation.html `font-feature-settings` [4]
+    * test_initial_storage.html `font-feature-settings` [6]
+    * test_value_storage.html `font-feature-settings` [112]
+  * font-language-override property
+    * test_compute_data_with_start_struct.html `font-language-override` [2]
+    * test_inherit_computation.html `font-language-override` [8]
+    * test_inherit_storage.html `font-language-override` [12]
+    * test_initial_computation.html `font-language-override` [4]
+    * test_initial_storage.html `font-language-override` [6]
+    * test_value_storage.html `font-language-override` [58]
+  * image-orientation property
+    * test_compute_data_with_start_struct.html `image-orientation` [2]
+    * test_inherit_computation.html `image-orientation` [4]
+    * test_inherit_storage.html `image-orientation` [4]
+    * test_initial_computation.html `image-orientation` [2]
+    * test_initial_storage.html `image-orientation` [2]
+    * test_value_storage.html `image-orientation` [80]
+* @page support
+  * test_bug887741_at-rules_in_declaration_lists.html [1]
+  * test_page_parser.html [30]
+  * test_rule_insertion.html `@page` [4]
+* Unsupported prefixed values
+  * moz-prefixed gradient functions bug 1337655
+    * test_value_storage.html `-moz-linear-gradient` [293]
+    * ... `-moz-radial-gradient` [309]
+    * ... `-moz-repeating-` [298]
+  * webkit-prefixed gradient functions servo/servo#15441
+    * test_value_storage.html `-webkit-gradient` [225]
+    * ... `-webkit-linear-gradient` [40]
+    * ... `-webkit-radial-gradient` [105]
+    * ... `-webkit-repeating-` [35]
+  * moz-prefixed intrinsic width values
+    * test_flexbox_flex_shorthand.html `-moz-fit-content` [2]
+    * test_value_storage.html `-moz-max-content` [52]
+    * ... `-moz-min-content` [12]
+    * ... `-moz-fit-content` [12]
+    * ... `-moz-available` [10]
+  * -moz-element() function for <image>
+    * test_value_storage.html `-moz-element` [49]
+  * -moz-anchor-decoration value on text-decoration
+    * test_value_storage.html `-moz-anchor-decoration` [10]
+  * various values on -{webkit,moz}-user-select servo/servo#15197
+    * test_value_storage.html `user-select` [18]
+  * -moz-default-background-color
+    * test_value_storage.html `-moz-default-background-color` [1]
+  * several prefixed values in cursor property
+    * test_value_storage.html `cursor` [4]
+  * moz-prefixed values of overflow shorthand bug 1330888
+    * test_bug319381.html [8]
+    * test_value_storage.html `'overflow` [8]
+  * -moz-middle-with-baseline on vertical-align
+    * test_value_storage.html `-moz-middle-with-baseline` [1]
+  * -moz-pre-space on white-space
+    * test_value_storage.html `-moz-pre-space` [1]
+  * -moz-crisp-edges on image-rendering
+    * test_value_storage.html `-moz-crisp-edges` [1]
+  * -webkit-{flex,inline-flex} for display servo/servo#15400
+    * test_webkit_flex_display.html [4]
+  * test_pixel_lengths.html `mozmm`: mozmm unit [3]
+* Unsupported values
+  * SVG-only values of pointer-events not recognized
+    * test_compute_data_with_start_struct.html `pointer-events` [2]
+    * test_inherit_computation.html `pointer-events` [4]
+    * test_initial_computation.html `pointer-events` [2]
+    * test_pointer-events.html [2]
+    * test_value_storage.html `pointer-events` [8]
+  * new syntax of rgba?() and hsla?() functions servo/rust-cssparser#113
+    * test_parse_rule.html `128.0` [1]
+    * test_value_storage.html `'color'` [37]
+    * ... `rgb(100, 100.0, 100)` [1]
+  * color interpolation hint not supported servo/servo#15166
+    * test_value_storage.html `'linear-gradient` [50]
+  * two-keyword form of background-repeat/mask-repeat servo/servo#14954
+    * test_value_storage.html `background-repeat` [14]
+    * ... `mask-repeat` [24]
+  * lack glue for function values of content property bug 1296477
+    * test_rule_insertion.html `decimal counter` [3]
+    * test_value_storage.html `'content` [38]
+  * SVG-in-OpenType values not supported servo/servo#15211
+    * test_value_storage.html `context-` [2]
+  * writing-mode: sideways-{lr,rl} and SVG values servo/servo#15213
+    * test_logical_properties.html `sideways` [1224]
+    * test_value_storage.html `writing-mode` [8]
+* Incorrect parsing
+  * calc() doesn't support dividing expression servo/servo#15192
+    * test_value_storage.html `calc(50px/` [7]
+    * ... `calc(2em / ` [9]
+  * calc() doesn't support number value servo/servo#15205
+    * test_value_storage.html `calc(1 +` [1]
+    * ... `calc(-2.5)` [1]
+  * incorrect parsing function for column-{gap,width} servo/servo#15088
+    * test_compute_data_with_start_struct.html ` column-` [4]
+    * test_value_storage.html `column-gap` [3]
+    * ... `column-width` [3]
+  * size part of shorthand background/mask always desires two values servo/servo#15199
+    * test_value_storage.html `'background'` [18]
+    * ... `/ auto none` [34]
+    * ... `/ auto repeat` [17]
+  * border shorthands do not reset border-image servo/servo#15202
+    * test_inherit_storage.html `for property 'border-image-` [5]
+    * test_initial_storage.html `for property 'border-image-` [10]
+    * test_value_storage.html `(for 'border-image-` [60]
+  * whitespace should be required around '+'/'-' servo/servo#15486
+    * test_property_syntax_errors.html `calc(2em+` [6]
+    * ... `calc(50%+` [8]
+  * <position> value accepts invalid 3-value forms servo/servo#15488
+    * test_property_syntax_errors.html `'background-position'` [12]
+    * ... `mask-position'` [20]
+    * ... `object-position` [4]
+    * ... `circle(at ` [2]
+    * ... `ellipse(at ` [2]
+  * accepts rubbish for second part of value:
+    * {transform,perspective}-origin servo/servo#15487
+      * test_property_syntax_errors.html `transform-origin'` [50]
+      * ... `perspective-origin'` [30]
+    * test_property_syntax_errors.html `'border-spacing'`: servo/servo#15489 [7]
+    * ... `'text-overflow'`: servo/servo#15491 [8]
+* Incorrect serialization
+  * border-radius and -moz-outline-radius shorthand servo/servo#15169
+    * test_priority_preservation.html `border-radius` [4]
+    * test_value_storage.html `border-radius:` [156]
+    * ... `-moz-outline-radius:` [76]
+    * test_shorthand_property_getters.html `should condense to shortest possible` [6]
+  * transform property servo/servo#15194
+    * test_value_storage.html `'transform` [104]
+    * ... `"transform` [66]
+    * ... `-webkit-transform` [109]
+    * test_specified_value_serialization.html [27]
+    * test_units_angle.html [3]
+  * test_value_storage.html `columns:`: servo/servo#15190 [32]
+  * {background,mask}-position lacks comma for serialization servo/servo#15200
+    * test_value_storage.html `background-position` [81]
+    * ... `for 'mask-position` [18]
+    * ... `for '-webkit-mask-position` [36]
+    * ... `for '-webkit-mask` [3]
+    * test_shorthand_property_getters.html `background-position` [3]
+  * box-shadow wrong order of <length> values servo/servo#15203
+    * test_value_storage.html `box-shadow` [44]
+  * outline shorthand generates "initial" as part servo/servo#15206
+    * test_value_storage.html `'outline:` [4]
+  * quotes empty value is not serialized to "none" servo/servo#15209
+    * test_value_storage.html `quotes` [3]
+  * border shorthand serializes when not Serializes servo/servo#15395
+    * test_shorthand_property_getters.html `should not be able to serialize border` [7]
+  * color value not canonicalized servo/servo#15397
+    * test_shorthand_property_getters.html `should condense to canonical case` [2]
+  * animation and transition shorthand serialization is wrong servo/servo#15398
+    * test_shorthand_property_getters.html `animation` [9]
+    * ... `transition` [5]
+  * background-position invalid 3-value form **issue to be filed**
+    * test_shorthand_property_getters.html `should serialize to 4-value` [2]
+  * test_variables.html `--weird`: name of custom property is not escaped properly servo/servo#15399 [1]
+  * ... `got "--`: CSS-wide keywords in custom properties servo/servo#15401 [3]
+* Unsupported pseudo-classes
+  * :default ##easy##
+    * test_bug302186.html [24]
+  * test_bug98997.html: pseudo-class :empty and :-moz-only-whitespace bug 1337068 [75]
+  * :lang() servo/servo#15415
+    * test_parse_rule.html `:lang` [2]
+  * :-moz-{first,last}-node
+    * test_selectors.html `:-moz-` [4]
+    * ... `unexpected rule index` [2]
+  * :placeholder-shown
+    * test_selectors.html `TypeError` [1]
+* issues arround font shorthand servo/servo#15032 servo/servo#15036
+  * test_bug377947.html [2]
+  * test_inherit_storage.html `for property 'font-` [2]
+  * test_initial_storage.html `for property 'font-` [1]
+  * test_value_storage.html `'font'` [171]
+  * test_shorthand_property_getters.html `font shorthand` [2]
+  * test_system_font_serialization.html [11]
+* test_value_storage.html `font-size: calc(`: clamp negative value servo/servo#15296 [4]
+* rounding issue
+  * test_value_storage.html `33.5833px` [2]
+  * ... `98.7667px` [1]
+  * ... `0.766667px` [2]
+  * ... `75.5667px` [2]
+  * ... `105.333px` [2]
+* test_viewport_units.html: viewport units support [12]
+* test_value_storage.html `: var(--a)`: extra whitespace is added for shorthand with variables servo/servo#15295 [*]
+* border-width computed wrong bug 1335990
+  * test_parse_rule.html `border-style` [4]
+  * test_initial_computation.html `0px", expected "3px` [48]
+* Negative value should be rejected
+  * test_property_syntax_errors.html `'-10%' not accepted for 'border-image-slice'`: negative percentage servo/servo#15339 [2]
+  * ... `transition-duration`: servo/servo#15343 [20]
+  * ... `-radius'`: servo/servo#15345 [30]
+  * ... `perspective'`: servo/servo#15337 [20]
+  * third length of shadow servo/servo#15490
+    * test_property_syntax_errors.html `box-shadow'` [6]
+    * ... `'text-shadow'` [2]
+    * ... `drop-shadow` [6]
+  * <shape-radius> servo/servo#15492
+    * test_property_syntax_errors.html `circle(-` [2]
+    * ... `ellipse(-` [4]
+    * ... `ellipse(20px -` [2]
+  * test_property_syntax_errors.html `(-1)`: factor value in filter functions servo/servo#15494 [42]
+* test_property_syntax_errors.html `transition-timing-function`: invalid range for cubic-bezier and steps servo/servo#15344 [60]
+* Quirks mode support
+  * hashless color servo/servo#15341
+    * test_property_syntax_errors.html `color: 000000` [22]
+    * ... `color: 96ed2a` [22]
+    * ... `color: fff` [4]
+  * unitless length servo/servo#15342
+    * test_property_syntax_errors.html ` 20 ` [6]
+    * ... `: 10 ` [6]
+    * ... ` 2 ` [26]
+    * ... `: 5 ` [84]
+    * ... `border-spacing: ` [5]
+    * ... `rect(1, ` [1]
+* test_pseudoelement_parsing.html: support parsing some pseudo-classes on some pseudo-elements [5]
+* Unit should be preserved after parsing servo/servo#15346
+  * test_units_length.html [5]
+  * test_units_time.html [1]
+* insertRule / deleteRule don't work bug 1336863
+  * test_rule_insertion.html [16]
+* @-moz-document support
+  * test_rule_serialization.html [2]
+* getComputedStyle style doesn't contain custom properties bug 1336891
+  * test_variable_serialization_computed.html [36]
+  * test_variables.html `custom property name` [2]
+* test_css_supports.html: issues around @supports syntax servo/servo#15482 [8]
+* test_load_events_on_stylesheets.html: stylesheets from data uri are not sync loaded [3]
+
+## Assertions
+
+* Table wrapper with borders and paddings bug 1324661
+  * test_animations_async_tests.html asserts [3]
+  * test_animations_effect_timing_enddelay.html asserts [2]
+  * test_animations_event_order.html asserts [1]
+  * test_animations_omta_start.html asserts [1]
+  * test_animations_playbackrate.html asserts [1]
+  * test_at_rule_parse_serialize.html asserts [1]
+  * test_unclosed_parentheses.html asserts [1]
+* Content glue not implemented
+  * assertion in frame constructor bug 1324704
+    * test_rule_insertion.html asserts [1]
+  * assertion in computed style bug 1337635
+    * test_value_cloning.html asserts [18]
+    * test_value_computation.html asserts [18]
+    * test_value_storage.html asserts [32]
+* test_value_cloning.html asserts: negative radius bug 1337618 [6]
+
+## Need Gecko change
+
+* Servo is correct but Gecko is wrong
+  * unitless zero as angle bug 1234357
+    * test_property_syntax_errors.html `linear-gradient(0,` [10]
+    * ... `hue-rotate(0)` [6]
+* test_moz_device_pixel_ratio.html: probably unship -moz-device-pixel-ratio bug 1338425 [4]
+
+## Spec Unclear
+
+* test_property_syntax_errors.html `'background'`: whether background shorthand should accept "text" [40]
+* test_inherit_computation.html `weight style`: whether font-synthesis should be reset by font w3c/csswg-drafts#1032 [8]
+
+## Unknown / Unsure
+
+* border-width/padding failure
+  * test_compute_data_with_start_struct.html `-width` [4]
+  * ... `padding-` [4]
+* -moz-border alias should have been fixed servo/servo#15297
+  * test_inherit_storage.html `-moz-border-` [22]
+  * ... `border-inline-` [2]
+  * test_inherit_computation.html `-moz-border-end` [12]
+  * ... `-moz-border-start` [12]
+  * test_initial_storage.html `-moz-border-` [44]
+  * ... `border-inline-` [4]
+  * test_initial_computation.html `-moz-border-end` [6]
+  * ... `-moz-border-start` [6]
+  * test_value_storage.html `-moz-border-end` [66]
+  * ... `border-inline-end` [42]
+  * ... `-moz-border-start` [66]
+  * ... `border-inline-start` [42]
+* test_selectors.html `:nth-child`: <an+b> parsing difference [14]
+* test_selectors_on_anonymous_content.html: xbl and :nth-child [1]
+* test_variables.html `url`: url in custom property [1]
+* test_pseudoelement_state.html: doesn't seem to work at all, but only range-thumb fails... [4]
+
+## Ignore
+
+* Ignore for now since should be mostly identical to test_value_storage.html
+  * test_value_cloning.html [*]
+  * test_value_computation.html [*]

--- a/testing/mochitest/mochitest_options.py
+++ b/testing/mochitest/mochitest_options.py
@@ -588,16 +588,22 @@ class MochitestArguments(ArgumentContain
           "help": "Delete pending crash reports before running tests.",
           "suppress": True,
           }],
         [["--websocket-process-bridge-port"],
          {"default": "8191",
           "dest": "websocket_process_bridge_port",
           "help": "Port for websocket/process bridge. Default 8191.",
           }],
+        [["--failure-pattern-file"],
+         {"default": None,
+          "dest": "failure_pattern_file",
+          "help": "File describes all failure patterns of the tests.",
+          "suppress": True,
+          }],
     ]
 
     defaults = {
         # Bug 1065098 - The geckomediaplugin process fails to produce a leak
         # log for some reason.
         'ignoreMissingLeaks': ["geckomediaplugin"],
         'extensionsToExclude': ['specialpowers'],
         # Set server information on the args object

--- a/testing/mochitest/runtests.py
+++ b/testing/mochitest/runtests.py
@@ -772,16 +772,18 @@ class MochitestDesktop(object):
     CHROME_PATH = "redirect.html"
     log = None
 
     certdbNew = False
     sslTunnel = None
     DEFAULT_TIMEOUT = 60.0
     mediaDevices = None
 
+    patternFiles = {}
+
     # XXX use automation.py for test name to avoid breaking legacy
     # TODO: replace this with 'runtests.py' or 'mochitest' or the like
     test_name = 'automation.py'
 
     def __init__(self, logger_options, quiet=False):
         self.update_mozinfo()
         self.server = None
         self.wsserver = None
@@ -1296,16 +1298,64 @@ toolbar#nav-bar {
         for test in tests:
             if 'disabled' in test:
                 self.log.test_start(test['path'])
                 self.log.test_end(
                     test['path'],
                     'SKIP',
                     message=test['disabled'])
 
+    def loadFailurePatternFile(self, pat_file):
+        if pat_file in self.patternFiles:
+            return self.patternFiles[pat_file]
+        if not os.path.isfile(pat_file):
+            self.log.error("TEST-UNEXPECTED-ERROR | runtests.py | "
+                           "Cannot find failure pattern file " + pat_file)
+            return None
+
+        # Using ":error" to ensure it shows up in the failure summary.
+        self.log.warning(
+            "[runtests.py:error] Using {} to filter failures. If there "
+            "is any number mismatch below, you could have fixed "
+            "something documented in that file. Please reduce the "
+            "failure count appropriately.".format(pat_file))
+        patternRE = re.compile(r"""
+            ^\s*\*\s*               # list bullet
+            (test_\S+|\.{3})        # test name
+            (?:\s*(`.+?`|asserts))? # failure pattern
+            (?::.+)?                # optional description
+            \s*\[(\d+|\*)\]         # expected count
+            \s*$
+        """, re.X)
+        patterns = {}
+        with open(pat_file) as f:
+            last_name = None
+            for line in f:
+                match = patternRE.match(line)
+                if not match:
+                    continue
+                name = match.group(1)
+                name = last_name if name == "..." else name
+                last_name = name
+                pat = match.group(2)
+                if pat is not None:
+                    pat = "ASSERTION" if pat == "asserts" else pat[1:-1]
+                count = match.group(3)
+                count = None if count == "*" else int(count)
+                if name not in patterns:
+                    patterns[name] = []
+                patterns[name].append((pat, count))
+        self.patternFiles[pat_file] = patterns
+        return patterns
+
+    def getFailurePatterns(self, pat_file, test_name):
+        patterns = self.loadFailurePatternFile(pat_file)
+        if patterns:
+            return patterns.get(test_name, None)
+
     def getActiveTests(self, options, disabled=True):
         """
           This method is used to parse the manifest and return active filtered tests.
         """
         if self._active_tests:
             return self._active_tests
 
         tests = []
@@ -1400,16 +1450,22 @@ toolbar#nav-bar {
 
             testob = {'path': tp}
             if 'disabled' in test:
                 testob['disabled'] = test['disabled']
             if 'expected' in test:
                 testob['expected'] = test['expected']
             if 'scheme' in test:
                 testob['scheme'] = test['scheme']
+            if options.failure_pattern_file:
+                pat_file = os.path.join(os.path.dirname(test['manifest']),
+                                        options.failure_pattern_file)
+                patterns = self.getFailurePatterns(pat_file, test['name'])
+                if patterns:
+                    testob['expected'] = patterns
             paths.append(testob)
 
         def path_sort(ob1, ob2):
             path1 = ob1['path'].split('/')
             path2 = ob2['path'].split('/')
             return cmp(path1, path2)
 
         paths.sort(path_sort)

--- a/testing/mochitest/tests/SimpleTest/SimpleTest.js
+++ b/testing/mochitest/tests/SimpleTest/SimpleTest.js
@@ -215,23 +215,56 @@ if (typeof(computedStyle) == 'undefined'
         return style.getPropertyValue(selectorCase);
     };
 }
 
 SimpleTest._tests = [];
 SimpleTest._stopOnLoad = true;
 SimpleTest._cleanupFunctions = [];
 SimpleTest._timeoutFunctions = [];
+SimpleTest._inChaosMode = false;
+// When using failure pattern file to filter unexpected issues,
+// SimpleTest.expected would be an array of [pattern, expected count],
+// and SimpleTest.num_failed would be an array of actual counts which
+// has the same length as SimpleTest.expected.
 SimpleTest.expected = 'pass';
 SimpleTest.num_failed = 0;
-SimpleTest._inChaosMode = false;
+
+function usesFailurePatterns() {
+  return Array.isArray(SimpleTest.expected);
+}
+
+/**
+ * Checks whether there is any failure pattern matches the given error
+ * message, and if found, bumps the counter of the failure pattern.
+ * Returns whether a matched failure pattern is found.
+ */
+function recordIfMatchesFailurePattern(name, diag) {
+  let index = SimpleTest.expected.findIndex(([pat, count]) => {
+    return pat == null ||
+      (typeof name == "string" && name.includes(pat)) ||
+      (typeof diag == "string" && diag.includes(pat));
+  });
+  if (index >= 0) {
+    SimpleTest.num_failed[index]++;
+    return true;
+  }
+  return false;
+}
 
 SimpleTest.setExpected = function () {
   if (parent.TestRunner) {
-    SimpleTest.expected = parent.TestRunner.expected;
+    if (!Array.isArray(parent.TestRunner.expected)) {
+      SimpleTest.expected = parent.TestRunner.expected;
+    } else {
+      // Assertions are checked by the runner.
+      SimpleTest.expected = parent.TestRunner.expected.filter(([pat]) => pat != "ASSERTION");
+      SimpleTest.num_failed = new Array(SimpleTest.expected.length);
+      SimpleTest.num_failed.fill(0);
+    }
   }
 }
 SimpleTest.setExpected();
 
 /**
  * Something like assert.
 **/
 SimpleTest.ok = function (condition, name, diag, stack = null) {
@@ -239,16 +272,22 @@ SimpleTest.ok = function (condition, nam
     var test = {'result': !!condition, 'name': name, 'diag': diag};
     if (SimpleTest.expected == 'fail') {
       if (!test.result) {
         SimpleTest.num_failed++;
         test.result = !test.result;
       }
       var successInfo = {status:"FAIL", expected:"FAIL", message:"TEST-KNOWN-FAIL"};
       var failureInfo = {status:"PASS", expected:"FAIL", message:"TEST-UNEXPECTED-PASS"};
+    } else if (!test.result && usesFailurePatterns()) {
+      if (recordIfMatchesFailurePattern(name, diag)) {
+        test.result = true;
+      }
+      var successInfo = {status:"FAIL", expected:"FAIL", message:"TEST-KNOWN-FAIL"};
+      var failureInfo = {status:"FAIL", expected:"PASS", message:"TEST-UNEXPECTED-FAIL"};
     } else {
       var successInfo = {status:"PASS", expected:"PASS", message:"TEST-PASS"};
       var failureInfo = {status:"FAIL", expected:"PASS", message:"TEST-UNEXPECTED-FAIL"};
     }
 
     if (condition) {
         stack = null;
     } else if (!stack) {
@@ -293,16 +332,24 @@ SimpleTest.doesThrow = function(fn, name
     } catch (ex) { gotException = true; }
     ok(gotException, name);
 };
 
 //  --------------- Test.Builder/Test.More todo() -----------------
 
 SimpleTest.todo = function(condition, name, diag) {
     var test = {'result': !!condition, 'name': name, 'diag': diag, todo: true};
+    if (test.result && usesFailurePatterns() &&
+        recordIfMatchesFailurePattern(name, diag)) {
+      // Flipping the result to false so we don't get unexpected result. There
+      // is no perfect way here. A known failure can trigger unexpected pass,
+      // in which case, tagging it as KNOWN-FAIL probably makes more sense than
+      // marking it PASS.
+      test.result = false;
+    }
     var successInfo = {status:"PASS", expected:"FAIL", message:"TEST-UNEXPECTED-PASS"};
     var failureInfo = {status:"FAIL", expected:"FAIL", message:"TEST-KNOWN-FAIL"};
     SimpleTest._logResult(test, successInfo, failureInfo);
     SimpleTest._tests.push(test);
 };
 
 /*
  * Returns the absolute URL to a test data file from where tests
@@ -1075,16 +1122,34 @@ SimpleTest.finish = function() {
     if (SimpleTest.expected == 'fail' && SimpleTest.num_failed <= 0) {
         msg = 'We expected at least one failure';
         var test = {'result': false, 'name': 'fail-if condition in manifest', 'diag': msg};
         var successInfo = {status:"FAIL", expected:"FAIL", message:"TEST-KNOWN-FAIL"};
         var failureInfo = {status:"PASS", expected:"FAIL", message:"TEST-UNEXPECTED-PASS"};
 
         SimpleTest._logResult(test, successInfo, failureInfo);
         SimpleTest._tests.push(test);
+    } else if (usesFailurePatterns()) {
+        SimpleTest.expected.forEach(([pat, expected_count], i) => {
+            let count = SimpleTest.num_failed[i];
+            let diag;
+            if (expected_count === null && count == 0) {
+                diag = "expected some failures but got none";
+            } else if (expected_count !== null && expected_count != count) {
+                diag = `expected ${expected_count} failures but got ${count}`;
+            } else {
+                return;
+            }
+            var name = pat ? `failure pattern \`${pat}\` in this test` : "failures in this test";
+            var test = {'result': false, name, diag};
+            var successInfo = {status:"PASS", expected:"PASS", message:"TEST-PASS"};
+            var failureInfo = {status:"FAIL", expected:"PASS", message:"TEST-UNEXPECTED-FAIL"};
+            SimpleTest._logResult(test, successInfo, failureInfo);
+            SimpleTest._tests.push(test);
+        });
     }
 
     SimpleTest._timeoutFunctions = [];
 
     SimpleTest.testsLength = SimpleTest._tests.length;
 
     SimpleTest._alreadyFinished = true;
 

--- a/testing/mochitest/tests/SimpleTest/TestRunner.js
+++ b/testing/mochitest/tests/SimpleTest/TestRunner.js
@@ -611,16 +611,24 @@ TestRunner.testUnloaded = function() {
     if (SpecialPowers.isDebugBuild) {
         var newAssertionCount = SpecialPowers.assertionCount();
         var numAsserts = newAssertionCount - TestRunner._lastAssertionCount;
         TestRunner._lastAssertionCount = newAssertionCount;
 
         var url = TestRunner.getNextUrl();
         var max = TestRunner._expectedMaxAsserts;
         var min = TestRunner._expectedMinAsserts;
+        if (Array.isArray(TestRunner.expected)) {
+            // Accumulate all assertion counts recorded in the failure pattern file.
+            let additionalAsserts = TestRunner.expected.reduce((acc, [pat, count]) => {
+                return pat == "ASSERTION" ? acc + count : acc;
+            });
+            min += additionalAsserts;
+            max += additionalAsserts;
+        }
         if (numAsserts > max) {
             TestRunner.structuredLogger.testEnd(url,
                                                 "ERROR",
                                                 "OK",
                                                 "Assertion count " + numAsserts + " is greater than expected range " +
                                                 min + "-" + max + " assertions.",
                                                 {assertions: numAsserts, min_asserts: min, max_asserts: max});
             TestRunner.updateUI([{ result: false }]);

--- a/testing/mozharness/configs/unittests/linux_unittest.py
+++ b/testing/mozharness/configs/unittests/linux_unittest.py
@@ -198,17 +198,17 @@ config = {
         "mochitest-gl": ["--subsuite=webgl"],
         "mochitest-devtools-chrome": ["--flavor=browser", "--subsuite=devtools"],
         "mochitest-devtools-chrome-chunked": ["--flavor=browser", "--subsuite=devtools", "--chunk-by-runtime"],
         "mochitest-devtools-chrome-coverage": ["--flavor=browser", "--subsuite=devtools", "--chunk-by-runtime", "--timeout=1200"],
         "jetpack-package": ["--flavor=jetpack-package"],
         "jetpack-package-clipboard": ["--flavor=jetpack-package", "--subsuite=clipboard"],
         "jetpack-addon": ["--flavor=jetpack-addon"],
         "a11y": ["--flavor=a11y"],
-        "mochitest-style": ["--disable-e10s", "layout/style/test"],
+        "mochitest-style": ["--disable-e10s", "--failure-pattern-file=stylo-failures.md", "layout/style/test"],
     },
     # local reftest suites
     "all_reftest_suites": {
         "crashtest": {
             "options": ["--suite=crashtest"],
             "tests": ["tests/reftest/tests/testing/crashtest/crashtests.list"]
         },
         "jsreftest": {