Bug 1210560 - Part 5: Convert BasicLayers usecases to PushGroupForBlendBack and temporary surfaces. r=jrmuizel

gfx/layers/basic/BasicLayersImpl.cpp

@@ -39,6 +39,25 @@ GetMaskData(Layer* aMaskLayer,
   return false;
 }
 
+already_AddRefed<SourceSurface>
+GetMaskForLayer(Layer* aLayer, Matrix* aMaskTransform)
+{
+  if (!aLayer->GetMaskLayer()) {
+    return nullptr;
+  }
+
+  MOZ_ASSERT(aMaskTransform);
+
+  AutoMoz2DMaskData mask;
+  if (GetMaskData(aLayer->GetMaskLayer(), Point(), &mask)) {
+    *aMaskTransform = mask.GetTransform();
+    RefPtr<SourceSurface> surf = mask.GetSurface();
+    return surf.forget();
+  }
+
+  return nullptr;
+}
+
 void
 PaintWithMask(gfxContext* aContext, float aOpacity, Layer* aMaskLayer)
 {