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

third_party/WebKit/Source/platform/graphics/paint/PaintController.cpp

 // 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.
 
 #include "platform/graphics/paint/PaintController.h"
 
 #include "platform/TraceEvent.h"
 #include "platform/graphics/GraphicsLayer.h"
 #include "platform/graphics/paint/DrawingDisplayItem.h"
 #include "third_party/skia/include/core/SkPictureAnalyzer.h"
@@ skipping 135 matching lines @@
         if (!indices.isEmpty() && indices.last() == (m_newDisplayItemList.size() - 1))
             indices.removeLast();
     }
 #endif
     m_newDisplayItemList.removeLast();
 
     if (RuntimeEnabledFeatures::slimmingPaintV2Enabled())
         m_newPaintChunks.decrementDisplayItemIndex();
 }
 
+const DisplayItem* PaintController::lastDisplayItem(unsigned offset)
+{
+    if (offset < m_newDisplayItemList.size())
+        return &m_newDisplayItemList[m_newDisplayItemList.size() - offset - 1];
+    return nullptr;
+}
+
 void PaintController::processNewItem(DisplayItem& displayItem)
 {
     DCHECK(!m_constructionDisabled);
 
 #if CHECK_DISPLAY_ITEM_CLIENT_ALIVENESS
     if (!isSkippingCache()) {
         if (displayItem.isCacheable()) {
             // Mark the client shouldKeepAlive under this PaintController.
             // The status will end after the new display items are committed.
             displayItem.client().beginShouldKeepAlive(this);
@@ skipping 387 matching lines @@
 
 void PaintController::showDebugData() const
 {
     WTFLogAlways("current display item list: [%s]\n", displayItemListAsDebugString(m_currentPaintArtifact.getDisplayItemList()).utf8().data());
     WTFLogAlways("new display item list: [%s]\n", displayItemListAsDebugString(m_newDisplayItemList).utf8().data());
 }
 
 #endif // ifndef NDEBUG
 
 } // namespace blink