Bug 1419508 - Return early from CreateMaskLayer if there is no visible data - r=mattwoodrow

MozReview-Commit-ID: 9jWGXA2eGvv

--HG--
extra : rebase_source : 1e14c7baa20cd3441de7fa4b7b9c4de574121a24

layout/painting/FrameLayerBuilder.cpp

@@ -6358,6 +6358,10 @@ ContainerState::CreateMaskLayer(Layer *aLayer,
   gfx::Rect boundingRect = CalculateBounds(newData.mRoundedClipRects,
                                            newData.mAppUnitsPerDevPixel);
   boundingRect.Scale(mParameters.mXScale, mParameters.mYScale);
+  if (boundingRect.IsEmpty()) {
+    // Return early if we know that there is effectively no visible data.
+    return nullptr;
+  }
 
   uint32_t maxSize = mManager->GetMaxTextureSize();
   NS_ASSERTION(maxSize > 0, "Invalid max texture size");