Slimming Paint phase 2 compositing algorithm plumbing

Source/platform/graphics/ContentLayerDelegate.cpp

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
  *     notice, this list of conditions and the following disclaimer in the
@@ skipping 72 matching lines @@
 }
 
 void ContentLayerDelegate::paintContents(
     WebDisplayItemList* webDisplayItemList, const WebRect& clip,
     WebContentLayerClient::PaintingControlSetting paintingControl)
 {
     TRACE_EVENT1("blink,benchmark", "ContentLayerDelegate::paintContents", "clip_rect", toTracedValue(clip));
 
     ASSERT(RuntimeEnabledFeatures::slimmingPaintEnabled());
 
+    // TODO(pdr): Remove when slimming paint v2 is further along. This is only
+    // here so the browser is usable during development and does not crash due
+    // to committing the new display items twice.
+    if (RuntimeEnabledFeatures::slimmingPaintV2Enabled()) {
+        if (m_painter->displayItemList()) {
+            for (auto& displayItem : m_painter->displayItemList()->displayItems())
+                displayItem.appendToWebDisplayItemList(webDisplayItemList);
+        }
+        return;
+    }
+
     DisplayItemList* displayItemList = m_painter->displayItemList();
     ASSERT(displayItemList);
     displayItemList->setDisplayItemConstructionIsDisabled(
         paintingControl == WebContentLayerClient::DisplayListConstructionDisabled);
 
     // We also disable caching when Painting or Construction are disabled. In both cases we would like
     // to compare assuming the full cost of recording, not the cost of re-using cached content.
     if (paintingControl != WebContentLayerClient::PaintDefaultBehavior)
         displayItemList->invalidateAll();
 
     GraphicsContext::DisabledMode disabledMode = GraphicsContext::NothingDisabled;
     if (paintingControl == WebContentLayerClient::DisplayListPaintingDisabled
         || paintingControl == WebContentLayerClient::DisplayListConstructionDisabled)
         disabledMode = GraphicsContext::FullyDisabled;
     GraphicsContext context(displayItemList, disabledMode);
 
     m_painter->paint(context, clip);
 
     displayItemList->commitNewDisplayItemsAndAppendToWebDisplayItemList(webDisplayItemList);
 }
 
 size_t ContentLayerDelegate::approximateUnsharedMemoryUsage() const
 {
     return m_painter->displayItemList()->approximateUnsharedMemoryUsage();
 }
 
 } // namespace blink