--- a/browser/base/content/test/general/browser.ini
+++ b/browser/base/content/test/general/browser.ini
@@ -294,20 +294,20 @@ skip-if = true # Disabled due to the cli
 [browser_contentAreaClick.js]
 skip-if = e10s # Clicks in content don't go through contentAreaClick with e10s.
 # DO NOT ADD MORE TESTS HERE. USE A TOPICAL DIRECTORY INSTEAD.
 [browser_contentAltClick.js]
 # DO NOT ADD MORE TESTS HERE. USE A TOPICAL DIRECTORY INSTEAD.
 [browser_contextmenu.js]
 subsuite = clipboard
 tags = fullscreen
-skip-if = toolkit == "gtk2" || toolkit == "gtk3" # disabled on Linux due to bug 513558
+skip-if = toolkit == "gtk3" # disabled on Linux due to bug 513558
 # DO NOT ADD MORE TESTS HERE. USE A TOPICAL DIRECTORY INSTEAD.
 [browser_contextmenu_input.js]
-skip-if = toolkit == "gtk2" || toolkit == "gtk3" # disabled on Linux due to bug 513558
+skip-if = toolkit == "gtk3" # disabled on Linux due to bug 513558
 # DO NOT ADD MORE TESTS HERE. USE A TOPICAL DIRECTORY INSTEAD.
 [browser_ctrlTab.js]
 # DO NOT ADD MORE TESTS HERE. USE A TOPICAL DIRECTORY INSTEAD.
 [browser_datachoices_notification.js]
 skip-if = !datareporting
 # DO NOT ADD MORE TESTS HERE. USE A TOPICAL DIRECTORY INSTEAD.
 [browser_decoderDoctor.js]
 # DO NOT ADD MORE TESTS HERE. USE A TOPICAL DIRECTORY INSTEAD.

--- a/browser/base/content/test/plugins/browser.ini
+++ b/browser/base/content/test/plugins/browser.ini
@@ -49,17 +49,17 @@ tags = blocklist
 [browser_bug797677.js]
 [browser_bug812562.js]
 tags = blocklist
 [browser_bug818118.js]
 [browser_bug820497.js]
 [browser_clearplugindata.js]
 tags = blocklist
 [browser_CTP_context_menu.js]
-skip-if = toolkit == "gtk2" || toolkit == "gtk3"   # fails intermittently on Linux (bug 909342)
+skip-if = toolkit == "gtk3"   # fails intermittently on Linux (bug 909342)
 tags = blocklist
 [browser_CTP_crashreporting.js]
 skip-if = !crashreporter
 tags = blocklist
 [browser_CTP_drag_drop.js]
 tags = blocklist
 [browser_CTP_favorfallback.js]
 [browser_CTP_hide_overlay.js]

--- a/docshell/test/chrome/chrome.ini
+++ b/docshell/test/chrome/chrome.ini
@@ -64,18 +64,16 @@ skip-if = true # bug 1393441
 [test_bug364461.xul]
 [test_bug396519.xul]
 [test_bug396649.xul]
 [test_bug428288.html]
 [test_bug449778.xul]
 [test_bug449780.xul]
 [test_bug453650.xul]
 [test_bug454235.xul]
-# bug 684176
-skip-if = toolkit == "gtk2"
 [test_bug456980.xul]
 [test_bug565388.xul]
 skip-if = os == 'linux' || os == 'mac' # Bug 1026815
 [test_bug582176.xul]
 [test_bug608669.xul]
 [test_bug662200.xul]
 [test_bug690056.xul]
 [test_bug789773.xul]

--- a/dom/ipc/tests/mochitest.ini
+++ b/dom/ipc/tests/mochitest.ini
@@ -10,16 +10,16 @@ skip-if = e10s
 skip-if = e10s
 [test_bug1086684.html]
 # This test is only supposed to run in the main process
 skip-if = e10s || toolkit == 'android'
 [test_cpow_cookies.html]
 [test_child_docshell.html]
 skip-if = toolkit == 'cocoa' || webrender # cocoa: disabled due to hangs, see changeset 6852e7c47edf, webrender: bug 1424752
 [test_CrashService_crash.html]
-skip-if = !(crashreporter && !e10s && (toolkit == 'gtk2' || toolkit == 'gtk3' || toolkit == 'cocoa' || toolkit == 'windows'))
+skip-if = !(crashreporter && !e10s && (toolkit == 'gtk3' || toolkit == 'cocoa' || toolkit == 'windows'))
 [test_temporaryfile_stream.html]
 skip-if = !e10s
 support-files =
   blob_verify.sjs
   !/dom/canvas/test/captureStream_common.js
 [test_Preallocated.html]
 skip-if = !e10s

--- a/dom/plugins/test/mochitest/mochitest.ini
+++ b/dom/plugins/test/mochitest/mochitest.ini
@@ -64,19 +64,19 @@ skip-if = toolkit == 'android' # needs p
 [test_bug1307694.html]
 [test_cocoa_focus.html]
 skip-if = toolkit != "cocoa" || e10s # Bug 1194534
 support-files = cocoa_focus.html
 [test_cocoa_window_focus.html]
 skip-if = toolkit != "cocoa" # Bug 1194534
 support-files = cocoa_window_focus.html
 [test_copyText.html]
-skip-if = (toolkit != "gtk2") && (toolkit != "gtk3")
+skip-if = toolkit != "gtk3"
 [test_crash_nested_loop.html]
-skip-if = (toolkit != "gtk2") && (toolkit != "gtk3")
+skip-if = toolkit != "gtk3"
 [test_crashing.html]
 skip-if = !crashreporter
 [test_crashing2.html]
 skip-if = (!crashreporter) || true # Bug 566049
 [test_CrashService_crash.html]
 skip-if = !crashreporter || e10s
 [test_CrashService_hang.html]
 skip-if = !crashreporter || e10s
@@ -101,19 +101,16 @@ skip-if = !crashreporter || e10s
 [test_npruntime_identifiers.html]
 [test_npruntime_npnevaluate.html]
 [test_npruntime_npninvoke.html]
 [test_npruntime_npninvokedefault.html]
 [test_object.html]
 skip-if = toolkit == 'android' # needs plugin support
 [test_painting.html]
 skip-if = (toolkit == "cocoa" && e10s) # bug 1252230
-[test_plugin_scroll_invalidation.html]
-skip-if = toolkit != "gtk2"
-support-files = plugin_scroll_invalidation.html
 [test_plugin_scroll_painting.html]
 skip-if = true # Bug 596491
 [test_pluginstream_err.html]
 [test_pluginstream_geturl.html]
 skip-if = true # Bug 1267432
 [test_pluginstream_geturlnotify.html]
 skip-if = true # Bug 1267432
 [test_pluginstream_post.html]
@@ -142,10 +139,10 @@ skip-if = e10s # Bug 1090576
 skip-if = toolkit == "cocoa"
 [test_windowed_invalidate.html]
 skip-if = os != "win"
 [test_windowless_flash.html]
 skip-if = !(os == "win" && processor == "x86_64")
 [test_windowless_ime.html]
 skip-if = os != "win"
 [test_x11_error_crash.html]
-skip-if = !crashreporter || e10s || ((toolkit != "gtk2") && (toolkit != "gtk3"))
+skip-if = !crashreporter || e10s || toolkit != "gtk3"
 [test_zero_opacity.html]

deleted file mode 100644
--- a/dom/plugins/test/mochitest/plugin_scroll_invalidation.html
+++ /dev/null
@@ -1,60 +0,0 @@
-<!DOCTYPE HTML>
-<html>
-<head>
-  <title>Test helper for plugin child widgets not being invalidated by scrolling</title>
-  <style>
-    body {
-      background: linear-gradient(red, black);
-      width: 200px;
-      height: 200px;
-    }
-    embed {
-      position:absolute;
-    }
-    embed#paint-waiter {
-      top: 0px;
-      left: 0px;
-      width: 0px;
-      height: 0px;
-    }
-    embed#e0 {
-      top: 70px;
-      left: 70px;
-      width: 10px;
-      height: 10px;
-    }
-    embed#e1 {
-      top: 60px;
-      left: 60px;
-      width: 10px;
-      height: 20px;
-    }
-    embed#e2 {
-      top: 60px;
-      left: 70px;
-      width: 20px;
-      height: 10px;
-    }
-    embed#e3 {
-      top: 70px;
-      left: 80px;
-      width: 10px;
-      height: 20px;
-    }
-    embed#e4 {
-      top: 80px;
-      left: 60px;
-      width: 20px;
-      height: 10px;
-    }
-  </style>
-</head>
-<body>
-  <embed id="paint-waiter" type="application/x-test" wmode="window">
-  <embed id="e0" type="application/x-test" wmode="window" class="scrolling"/>
-  <embed id="e1" type="application/x-test" wmode="window" class="scrolling"/>
-  <embed id="e2" type="application/x-test" wmode="window" class="scrolling"/>
-  <embed id="e3" type="application/x-test" wmode="window" class="scrolling"/>
-  <embed id="e4" type="application/x-test" wmode="window" class="scrolling"/>
-</body>
-</html>

--- a/layout/generic/test/mochitest.ini
+++ b/layout/generic/test/mochitest.ini
@@ -106,17 +106,17 @@ skip-if = os=='win'
 [test_invalidate_during_plugin_paint.html]
 skip-if = toolkit == 'android' || webrender # webrender: see bug 1424752
 [test_intrinsic_size_on_loading.html]
 [test_movement_by_characters.html]
 [test_movement_by_words.html]
 # Disable the caret movement by word test on Linux because the shortcut keys
 # are defined in system level.  So, it depends on the environment.
 # Disable on Windows for too many intermittent failures (bug 916143).
-skip-if = (toolkit == "gtk2") || (toolkit == "gtk3") || (os == "win")
+skip-if = (toolkit == "gtk3") || (os == "win")
 [test_overflow_event.html]
 [test_page_scroll_with_fixed_pos.html]
 support-files = page_scroll_with_fixed_pos_window.html
 [test_plugin_clipping.xhtml]
 skip-if = e10s
 [test_plugin_clipping2.xhtml]
 skip-if = e10s
 [test_plugin_clipping_transformed.xhtml]

--- a/layout/reftests/forms/textarea/reftest.list
+++ b/layout/reftests/forms/textarea/reftest.list
@@ -1,14 +1,14 @@
 skip-if(Android) == resize.html resize-ref.html
 # an offset seems to apply to the native resizer on windows so skip this test for now
 skip-if(Android) skip-if(winWidget) fuzzy-if(cocoaWidget,1,33) fuzzy-if(skiaContent&&!winWidget&&!Android,5,10) == resize-background.html resize-background-ref.html
 skip-if(Android) != ltr.html rtl.html
 skip-if(Android) != ltr-scrollbar.html rtl-scrollbar.html
 skip-if(Android) != in-ltr-doc-scrollbar.html in-rtl-doc-scrollbar.html
 skip-if(Android) != ltr.html no-resize.html
-skip-if(Android) fails-if(xulRuntime.widgetToolkit=="gtk2") != rtl.html no-resize.html # bug 834724
+skip-if(Android) != rtl.html no-resize.html # bug 834724
 fuzzy-if(skiaContent,1,1) == rtl.html rtl-dynamic-attr.html
 fuzzy-if(skiaContent,1,1) == rtl.html rtl-dynamic-style.html
 == rtl.html in-dynamic-rtl-doc.html
 fuzzy-if(skiaContent,1,3) == setvalue-framereconstruction-1.html setvalue-framereconstruction-ref.html
 fuzzy-if(asyncPan&&!layersGPUAccelerated,102,4168) fails-if(webrender) == padding-scrollbar-placement.html padding-scrollbar-placement-ref.html
 == various-cols.html various-cols-ref.html

--- a/layout/tools/reftest/manifest.jsm
+++ b/layout/tools/reftest/manifest.jsm
@@ -485,18 +485,17 @@ function BuildConditionSandbox(aURL) {
     sandbox.layerChecksEnabled = !sandbox.webrender;
 
     sandbox.retainedDisplayList =
       prefs.getBoolPref("layout.display-list.retain");
 
     // Shortcuts for widget toolkits.
     sandbox.Android = xr.OS == "Android";
     sandbox.cocoaWidget = xr.widgetToolkit == "cocoa";
-    sandbox.gtkWidget = xr.widgetToolkit == "gtk2"
-                        || xr.widgetToolkit == "gtk3";
+    sandbox.gtkWidget = xr.widgetToolkit == "gtk3";
     sandbox.qtWidget = xr.widgetToolkit == "qt";
     sandbox.winWidget = xr.widgetToolkit == "windows";
 
     // Scrollbars that are semi-transparent. See bug 1169666.
     sandbox.transparentScrollbars = xr.widgetToolkit == "gtk3";
 
     if (sandbox.Android) {
         var sysInfo = CC["@mozilla.org/system-info;1"].getService(CI.nsIPropertyBag2);

--- a/python/mozbuild/mozbuild/test/test_mozinfo.py
+++ b/python/mozbuild/mozbuild/test/test_mozinfo.py
@@ -53,31 +53,31 @@ class TestBuildDict(unittest.TestCase, B
         self.assertEqual('x86', d['processor'])
         self.assertEqual('windows', d['toolkit'])
         self.assertEqual(32, d['bits'])
 
     def test_linux(self):
         d = build_dict(self._config(dict(
             OS_TARGET='Linux',
             TARGET_CPU='i386',
-            MOZ_WIDGET_TOOLKIT='gtk2',
+            MOZ_WIDGET_TOOLKIT='gtk3',
         )))
         self.assertEqual('linux', d['os'])
         self.assertEqual('x86', d['processor'])
-        self.assertEqual('gtk2', d['toolkit'])
+        self.assertEqual('gtk3', d['toolkit'])
         self.assertEqual(32, d['bits'])
 
         d = build_dict(self._config(dict(
             OS_TARGET='Linux',
             TARGET_CPU='x86_64',
-            MOZ_WIDGET_TOOLKIT='gtk2',
+            MOZ_WIDGET_TOOLKIT='gtk3',
         )))
         self.assertEqual('linux', d['os'])
         self.assertEqual('x86_64', d['processor'])
-        self.assertEqual('gtk2', d['toolkit'])
+        self.assertEqual('gtk3', d['toolkit'])
         self.assertEqual(64, d['bits'])
 
     def test_mac(self):
         d = build_dict(self._config(dict(
             OS_TARGET='Darwin',
             TARGET_CPU='i386',
             MOZ_WIDGET_TOOLKIT='cocoa',
         )))
@@ -127,24 +127,24 @@ class TestBuildDict(unittest.TestCase, B
 
     def test_arm(self):
         """
         Test that all arm CPU architectures => arm.
         """
         d = build_dict(self._config(dict(
             OS_TARGET='Linux',
             TARGET_CPU='arm',
-            MOZ_WIDGET_TOOLKIT='gtk2',
+            MOZ_WIDGET_TOOLKIT='gtk3',
         )))
         self.assertEqual('arm', d['processor'])
 
         d = build_dict(self._config(dict(
             OS_TARGET='Linux',
             TARGET_CPU='armv7',
-            MOZ_WIDGET_TOOLKIT='gtk2',
+            MOZ_WIDGET_TOOLKIT='gtk3',
         )))
         self.assertEqual('arm', d['processor'])
 
     def test_unknown(self):
         """
         Test that unknown values pass through okay.
         """
         d = build_dict(self._config(dict(
@@ -160,43 +160,43 @@ class TestBuildDict(unittest.TestCase, B
 
     def test_debug(self):
         """
         Test that debug values are properly detected.
         """
         d = build_dict(self._config(dict(
             OS_TARGET='Linux',
             TARGET_CPU='i386',
-            MOZ_WIDGET_TOOLKIT='gtk2',
+            MOZ_WIDGET_TOOLKIT='gtk3',
         )))
         self.assertEqual(False, d['debug'])
 
         d = build_dict(self._config(dict(
             OS_TARGET='Linux',
             TARGET_CPU='i386',
-            MOZ_WIDGET_TOOLKIT='gtk2',
+            MOZ_WIDGET_TOOLKIT='gtk3',
             MOZ_DEBUG='1',
         )))
         self.assertEqual(True, d['debug'])
 
     def test_crashreporter(self):
         """
         Test that crashreporter values are properly detected.
         """
         d = build_dict(self._config(dict(
             OS_TARGET='Linux',
             TARGET_CPU='i386',
-            MOZ_WIDGET_TOOLKIT='gtk2',
+            MOZ_WIDGET_TOOLKIT='gtk3',
         )))
         self.assertEqual(False, d['crashreporter'])
 
         d = build_dict(self._config(dict(
             OS_TARGET='Linux',
             TARGET_CPU='i386',
-            MOZ_WIDGET_TOOLKIT='gtk2',
+            MOZ_WIDGET_TOOLKIT='gtk3',
             MOZ_CRASHREPORTER='1',
         )))
         self.assertEqual(True, d['crashreporter'])
 
 
 class TestWriteMozinfo(unittest.TestCase, Base):
     """
     Test the write_mozinfo function.

--- a/testing/mozbase/manifestparser/tests/test_testmanifest.py
+++ b/testing/mozbase/manifestparser/tests/test_testmanifest.py
@@ -29,17 +29,17 @@ class TestTestManifest(unittest.TestCase
                                                                    exists=False)],
                          ['fleem', 'linuxtest'])
 
         # Look for existing tests.  There is only one:
         self.assertEqual([i['name'] for i in manifest.active_tests()],
                          ['fleem'])
 
         # You should be able to expect failures:
-        last = manifest.active_tests(exists=False, toolkit='gtk2')[-1]
+        last = manifest.active_tests(exists=False, toolkit='gtk3')[-1]
         self.assertEqual(last['name'], 'linuxtest')
         self.assertEqual(last['expected'], 'pass')
         last = manifest.active_tests(exists=False, toolkit='cocoa')[-1]
         self.assertEqual(last['expected'], 'fail')
 
     def test_missing_paths(self):
         """
         Test paths that don't exist raise an exception in strict mode.

--- a/widget/headless/tests/xpcshell.ini
+++ b/widget/headless/tests/xpcshell.ini
@@ -1,9 +1,9 @@
 [DEFAULT]
-skip-if = toolkit != "gtk2" && toolkit != "gtk3" && toolkit != "windows"
+skip-if = toolkit != "gtk3" && toolkit != "windows"
 headless = true
 
 [test_headless_clipboard.js]
 [test_headless.js]
 support-files =
   headless.html
   headless_button.html