Bug 1231643 - Part 1. Create skia-A8-surface for mask composition when backendtype of the source DrawTarget is CG; r=mstange

MozReview-Commit-ID: J0oIhhTowk7

--HG--
extra : rebase_source : 0825caa3824a369d4a59a2ed8dc1c877bb4b0509

layout/svg/nsSVGIntegrationUtils.cpp

@@ -567,7 +567,17 @@ nsSVGIntegrationUtils::PaintFramesWithEffects(gfxContext& aContext,
         clipRect = aContext.GetClipExtents();
       }
       IntRect drawRect = RoundedOut(ToRect(clipRect));
-      RefPtr<DrawTarget> targetDT = aContext.GetDrawTarget()->CreateSimilarDrawTarget(drawRect.Size(), SurfaceFormat::A8);
+
+      // Mask composition result on CoreGraphic::A8 surface is not correct
+      // when mask-mode is not add(source over). Switch to skia when CG backend
+      // detected.
+      RefPtr<DrawTarget> targetDT =
+        (aContext.GetDrawTarget()->GetBackendType() == BackendType::COREGRAPHICS) ?
+          Factory::CreateDrawTarget(BackendType::SKIA, drawRect.Size(),
+                                    SurfaceFormat::A8) :
+          aContext.GetDrawTarget()->CreateSimilarDrawTarget(drawRect.Size(),
+                                                            SurfaceFormat::A8);
+
       if (!targetDT || !targetDT->IsValid()) {
         aContext.Restore();
         return;