Calculate and track display item opaqueness

third_party/WebKit/Source/platform/graphics/compositing/PaintArtifactCompositor.cpp

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "platform/graphics/compositing/PaintArtifactCompositor.h"
 
 #include "cc/layers/content_layer_client.h"
 #include "cc/layers/layer.h"
 #include "cc/layers/layer_settings.h"
 #include "cc/layers/picture_layer.h"
@@ skipping 122 matching lines @@
         gfx::Rect combinedBounds = enclosingIntRect(paintChunk.bounds);
         scoped_refptr<cc::DisplayItemList> displayList = recordPaintChunk(paintArtifact, paintChunk, combinedBounds);
         OwnPtr<ContentLayerClientImpl> contentLayerClient = adoptPtr(
             new ContentLayerClientImpl(std::move(displayList), gfx::Rect(combinedBounds.size())));
 
         scoped_refptr<cc::PictureLayer> layer = cc::PictureLayer::Create(cc::LayerSettings(), contentLayerClient.get());
         layer->SetPosition(gfx::PointF(combinedBounds.origin()));
         layer->SetBounds(combinedBounds.size());
         layer->SetTransform(transformToRoot(paintChunk.properties.transform.get()));
         layer->SetIsDrawable(true);
+        if (paintChunk.knownToBeOpaque)
+            layer->SetContentsOpaque(true);
         layer->SetNeedsDisplay();
 
         m_contentLayerClients.append(contentLayerClient.release());
         m_rootLayer->AddChild(std::move(layer));
     }
 }
 
 } // namespace blink