Fold compositing display items into contained drawings if the drawing is a singleton.

third_party/WebKit/Source/platform/graphics/paint/CompositingDisplayItem.h

 // Copyright 2014 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.
 
 #ifndef CompositingDisplayItem_h
 #define CompositingDisplayItem_h
 
 #include "platform/geometry/FloatRect.h"
 #include "platform/graphics/GraphicsTypes.h"
 #include "platform/graphics/paint/DisplayItem.h"
@@ skipping 12 matching lines @@
         , m_opacity(opacity)
         , m_hasBounds(bounds)
         , m_colorFilter(colorFilter)
     {
         if (bounds)
             m_bounds = FloatRect(*bounds);
     }
 
     void replay(GraphicsContext&) const override;
     void appendToWebDisplayItemList(const IntRect&, WebDisplayItemList*) const override;
+    bool isBeginCompositingDisplayItem() const final { return true; }

[f(malita), 2016/07/26 19:03:15]

Nit: 'final' is redundant (class is final).

[chrishtr, 2016/07/26 19:54:24]

Acknowledged.

 
 private:
 #ifndef NDEBUG
     void dumpPropertiesAsDebugString(WTF::StringBuilder&) const override;
 #endif
 #if ENABLE(ASSERT)
     bool equals(const DisplayItem& other) const final
     {
         return DisplayItem::equals(other)
             && m_xferMode == static_cast<const BeginCompositingDisplayItem&>(other).m_xferMode
@@ skipping 21 matching lines @@
 
 private:
 #if ENABLE(ASSERT)
     bool isEndAndPairedWith(DisplayItem::Type otherType) const final { return otherType == BeginCompositing; }
 #endif
 };
 
 } // namespace blink
 
 #endif // CompositingDisplayItem_h