Slimming Paint phase 2 compositing algorithm plumbing & skeleton display list API.

Source/platform/graphics/paint/DisplayItemList.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 "config.h"
 #include "platform/graphics/paint/DisplayItemList.h"
 
 #include "platform/NotImplemented.h"
 #include "platform/RuntimeEnabledFeatures.h"
 #include "platform/TraceEvent.h"
@@ skipping 198 matching lines @@
 // repainted ones, and appending new items.
 // - For CachedDisplayItem, copy the corresponding cached DrawingDisplayItem;
 // - FIXME: Re-enable SubtreeCachedDisplayItem:
 //   For SubtreeCachedDisplayItem, copy the cached display items between the
 //   corresponding BeginSubtreeDisplayItem and EndSubtreeDisplayItem (incl.);
 // - Otherwise, copy the new display item.
 //
 // The algorithm is O(|m_currentDisplayItems| + |m_newDisplayItems|).
 // Coefficients are related to the ratio of out-of-order [Subtree]CachedDisplayItems
 // and the average number of (Drawing|BeginSubtree)DisplayItems per client.
-void DisplayItemList::commitNewDisplayItems()
+// TODO(chrishtr); implement filling of displayListDiff.
+void DisplayItemList::commitNewDisplayItems(DisplayListDiff* displayListDiff)
 {
     TRACE_EVENT2("blink,benchmark", "DisplayItemList::commitNewDisplayItems", "current_display_list_size", (int)m_currentDisplayItems.size(),
         "num_non_cached_new_items", (int)m_newDisplayItems.size() - m_numCachedItems);
 
     // These data structures are used during painting only.
     m_clientScopeIdMap.clear();
     ASSERT(m_scopeStack.isEmpty());
     m_scopeStack.clear();
     ASSERT(!skippingCache());
 #if ENABLE(ASSERT)
@@ skipping 291 matching lines @@
 
 void DisplayItemList::replay(GraphicsContext& context)
 {
     TRACE_EVENT0("blink,benchmark", "DisplayItemList::replay");
     ASSERT(m_newDisplayItems.empty());
     for (auto displayItem : m_currentDisplayItems)
         displayItem->replay(context);
 }
 
 } // namespace blink