Backed out changeset e41148de8adf (bug 1531417) for failing at /browser_tabclose.js on a CLOSED TREE.

dom/canvas/CanvasRenderingContext2D.cpp

@@ -1354,13 +1354,6 @@ bool CanvasRenderingContext2D::TrySharedTarget(
     return false;
   }
 
-#ifdef XP_WIN
-  // Bug 1285271 - Disable shared buffer provider on Windows with D2D due to instability
-  if (gfxPlatform::GetPlatform()->GetPreferredCanvasBackend() == BackendType::DIRECT2D1_1) {
-    return false;
-  }
-#endif
-
   RefPtr<LayerManager> layerManager =
       LayerManagerFromCanvasElement(mCanvasElement);
 

modules/libpref/init/all.js

@@ -5082,6 +5082,15 @@ pref("layers.prefer-opengl", false);
 // Copy-on-write canvas
 pref("layers.shared-buffer-provider.enabled", true);
 
+#ifdef XP_WIN
+pref("layers.shared-buffer-provider.enabled", false);
+#endif
+
+#ifdef XP_MACOSX
+// cf. Bug 1324908
+pref("layers.shared-buffer-provider.enabled", false);
+#endif
+
 // Force all possible layers to be always active layers
 pref("layers.force-active", false);