Bug 1480139 - Disable tiling on linux due to high crash rate. r=jrmuizel

We're experiencing a high volume of content crashes on linux, most likely due to
free type thread unsafety seen in bug 1477444 and 1479498. This commit disables
tiling to stop the crashes for now while we investigate further.

--HG--
extra : rebase_source : 9becf3d4c5e41eb6a30ed12008ed342663660291
extra : intermediate-source : b9b178105f1bd1d794e53c2fb128bd9e505f8f32
extra : source : d28438c3e7596af6d6e482f3b227c7cb43dbbf26

layout/reftests/text-stroke/reftest.list

@@ -3,7 +3,7 @@
 default-preferences pref(layout.css.prefixes.webkit,true)
 
 fuzzy-if(gtkWidget,255,20) fuzzy-if(winWidget,20,10) fails-if(skiaContent&&(gtkWidget||winWidget)) == webkit-text-stroke-property-001.html webkit-text-stroke-property-001-ref.html
-fuzzy-if(gtkWidget,255,20) fuzzy-if(winWidget,20,10) == webkit-text-stroke-property-002.html webkit-text-stroke-property-002-ref.html
+fuzzy-if(gtkWidget,255,20) fuzzy-if(winWidget,20,10) fails-if(skiaContent&&!webrender&&gtkWidget) == webkit-text-stroke-property-002.html webkit-text-stroke-property-002-ref.html
 fuzzy-if(gtkWidget,255,20) fuzzy-if(winWidget,20,10) fails-if(skiaContent&&gtkWidget) == webkit-text-stroke-property-003.html webkit-text-stroke-property-003-ref.html
 fuzzy-if(gtkWidget,255,20) fuzzy-if(winWidget,20,10) fails-if(skiaContent&&gtkWidget) == webkit-text-stroke-property-004.html webkit-text-stroke-property-004-ref.html
 fuzzy-if(gtkWidget,255,20) fuzzy-if(winWidget,20,10) fails-if(skiaContent&&(gtkWidget||winWidget)) == webkit-text-stroke-property-005.html webkit-text-stroke-property-005-ref.html

modules/libpref/init/all.js

@@ -4841,7 +4841,7 @@ pref("layers.max-active", -1);
 // 0  -> full-tilt mode: Recomposite even if not transaction occured.
 pref("layers.offmainthreadcomposition.frame-rate", -1);
 
-#if defined(XP_MACOSX) || defined(MOZ_WIDGET_GTK)
+#if defined(XP_MACOSX)
 pref("layers.enable-tiles", true);
 #else
 pref("layers.enable-tiles", false);

testing/web-platform/meta/css/CSS2/backgrounds/background-position-001.xht.ini

@@ -1,3 +0,0 @@
-[background-position-001.xht]
-  expected:
-    if (os == "linux") and not webrender: FAIL

testing/web-platform/meta/css/CSS2/backgrounds/background-position-002.xht.ini

@@ -1,3 +0,0 @@
-[background-position-002.xht]
-  expected:
-    if (os == "linux") and not webrender: FAIL

testing/web-platform/meta/css/css-transforms/transform3d-preserve3d-013.html.ini

@@ -1,5 +1,3 @@
 [transform3d-preserve3d-013.html]
   expected:
     if webrender: FAIL
-  disabled:
-    if debug and not e10s and (os == "linux"): https://bugzilla.mozilla.org/show_bug.cgi?id=1471704