new file mode 100644
--- /dev/null
+++ b/browser/config/mozconfigs/linux64/stylo
@@ -0,0 +1,3 @@
+. "$topsrcdir/browser/config/mozconfigs/linux64/nightly"
+
+ac_add_options --enable-stylo

new file mode 100644
--- /dev/null
+++ b/browser/config/mozconfigs/linux64/stylo-debug
@@ -0,0 +1,3 @@
+. "$topsrcdir/browser/config/mozconfigs/linux64/debug"
+
+ac_add_options --enable-stylo

new file mode 100644
--- /dev/null
+++ b/testing/mozharness/configs/builds/releng_sub_linux_configs/64_stylo.py
@@ -0,0 +1,43 @@
+import os
+
+MOZ_OBJDIR = 'obj-firefox'
+
+config = {
+    'default_actions': [
+        'clobber',
+        'clone-tools',
+        'checkout-sources',
+        'setup-mock',
+        'build',
+        'upload-files',
+        'sendchange',
+        'check-test',
+        # 'generate-build-stats',
+        'update',  # decided by query_is_nightly()
+    ],
+    'stage_platform': 'linux64-stylo',
+    'enable_signing': False,
+    'enable_talos_sendchange': False,
+    #### 64 bit build specific #####
+    'env': {
+        'MOZBUILD_STATE_PATH': os.path.join(os.getcwd(), '.mozbuild'),
+        'MOZ_AUTOMATION': '1',
+        'DISPLAY': ':2',
+        'HG_SHARE_BASE_DIR': '/builds/hg-shared',
+        'MOZ_OBJDIR': MOZ_OBJDIR,
+        'MOZ_CRASHREPORTER_NO_REPORT': '1',
+        'CCACHE_DIR': '/builds/ccache',
+        'CCACHE_COMPRESS': '1',
+        'CCACHE_UMASK': '002',
+        'LC_ALL': 'C',
+        'XPCOM_DEBUG_BREAK': 'stack-and-abort',
+        # 64 bit specific
+        'PATH': '/tools/buildbot/bin:/usr/local/bin:/usr/lib64/ccache:/bin:\
+/usr/bin:/usr/local/sbin:/usr/sbin:/sbin:/tools/git/bin:/tools/python27/bin:\
+/tools/python27-mercurial/bin:/home/cltbld/bin',
+        'LD_LIBRARY_PATH': '/tools/gcc-4.3.3/installed/lib64:\
+%s/dist/bin' % (MOZ_OBJDIR,),
+        'TINDERBOX_OUTPUT': '1',
+    },
+    'src_mozconfig': 'browser/config/mozconfigs/linux64/stylo',
+}

new file mode 100644
--- /dev/null
+++ b/testing/mozharness/configs/builds/releng_sub_linux_configs/64_stylo_debug.py
@@ -0,0 +1,43 @@
+import os
+
+MOZ_OBJDIR = 'obj-firefox'
+
+config = {
+    'default_actions': [
+        'clobber',
+        'clone-tools',
+        'checkout-sources',
+        'setup-mock',
+        'build',
+        'upload-files',
+        'sendchange',
+        'check-test',
+        # 'generate-build-stats',
+        'update',  # decided by query_is_nightly()
+    ],
+    'stage_platform': 'linux64-stylo-debug',
+    'debug_build': True,
+    'enable_signing': False,
+    'enable_talos_sendchange': False,
+    'env': {
+        'MOZBUILD_STATE_PATH': os.path.join(os.getcwd(), '.mozbuild'),
+        'MOZ_AUTOMATION': '1',
+        'DISPLAY': ':2',
+        'HG_SHARE_BASE_DIR': '/builds/hg-shared',
+        'MOZ_OBJDIR': MOZ_OBJDIR,
+        'MOZ_CRASHREPORTER_NO_REPORT': '1',
+        'CCACHE_DIR': '/builds/ccache',
+        'CCACHE_COMPRESS': '1',
+        'CCACHE_UMASK': '002',
+        'LC_ALL': 'C',
+        'XPCOM_DEBUG_BREAK': 'stack-and-abort',
+        # 64 bit specific
+        'PATH': '/tools/buildbot/bin:/usr/local/bin:/usr/lib64/ccache:/bin:\
+/usr/bin:/usr/local/sbin:/usr/sbin:/sbin:/tools/git/bin:/tools/python27/bin:\
+/tools/python27-mercurial/bin:/home/cltbld/bin',
+        'LD_LIBRARY_PATH': '/tools/gcc-4.3.3/installed/lib64:\
+%s/dist/bin' % (MOZ_OBJDIR,),
+        'TINDERBOX_OUTPUT': '1',
+    },
+    'src_mozconfig': 'browser/config/mozconfigs/linux64/stylo-debug',
+}

--- a/testing/mozharness/configs/unittests/linux_unittest.py
+++ b/testing/mozharness/configs/unittests/linux_unittest.py
@@ -218,16 +218,21 @@ config = {
         "reftest": {
             "options": ["--suite=reftest"],
             "tests": ["tests/reftest/tests/layout/reftests/reftest.list"]
         },
         "reftest-no-accel": {
             "options": ["--suite=reftest",
                         "--setpref=layers.acceleration.force-enabled=disabled"],
             "tests": ["tests/reftest/tests/layout/reftests/reftest.list"]},
+        "reftest-stylo": {
+            "options": ["--suite=reftest",
+                        "--disable-e10s"],
+            "tests": ["tests/reftest/tests/layout/reftests/reftest-stylo.list"],
+        },
     },
     "all_xpcshell_suites": {
         "xpcshell": {
             "options": ["--xpcshell=%(abs_app_dir)s/" + XPCSHELL_NAME,
                         "--manifest=tests/xpcshell/tests/xpcshell.ini"],
             "tests": []
         },
         "xpcshell-addons": {

--- a/testing/mozharness/mozharness/mozilla/building/buildbase.py
+++ b/testing/mozharness/mozharness/mozilla/building/buildbase.py
@@ -350,16 +350,18 @@ class BuildOptionParser(object):
         'cross-debug': 'builds/releng_sub_%s_configs/%s_cross_debug.py',
         'cross-opt': 'builds/releng_sub_%s_configs/%s_cross_opt.py',
         'debug': 'builds/releng_sub_%s_configs/%s_debug.py',
         'asan-and-debug': 'builds/releng_sub_%s_configs/%s_asan_and_debug.py',
         'asan-tc-and-debug': 'builds/releng_sub_%s_configs/%s_asan_tc_and_debug.py',
         'stat-and-debug': 'builds/releng_sub_%s_configs/%s_stat_and_debug.py',
         'code-coverage': 'builds/releng_sub_%s_configs/%s_code_coverage.py',
         'source': 'builds/releng_sub_%s_configs/%s_source.py',
+        'stylo': 'builds/releng_sub_%s_configs/%s_stylo.py',
+        'stylo-debug': 'builds/releng_sub_%s_configs/%s_stylo_debug.py',
         'api-15-gradle-dependencies': 'builds/releng_sub_%s_configs/%s_api_15_gradle_dependencies.py',
         'api-15': 'builds/releng_sub_%s_configs/%s_api_15.py',
         'api-15-debug': 'builds/releng_sub_%s_configs/%s_api_15_debug.py',
         'api-15-gradle': 'builds/releng_sub_%s_configs/%s_api_15_gradle.py',
         'x86': 'builds/releng_sub_%s_configs/%s_x86.py',
         'api-15-partner-sample1': 'builds/releng_sub_%s_configs/%s_api_15_partner_sample1.py',
         'android-test': 'builds/releng_sub_%s_configs/%s_test.py',
         'android-checkstyle': 'builds/releng_sub_%s_configs/%s_checkstyle.py',