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

Source/core/compositing/DisplayListCompositingBuilder.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 "core/compositing/DisplayListCompositingBuilder.h"
+
+#include "platform/graphics/paint/DisplayItemTransformTreeBuilder.h"
+#include "platform/graphics/paint/DisplayList.h"
+
+namespace blink {
+
+void DisplayListCompositingBuilder::build()
+{
+    DisplayItemTransformTreeBuilder transformTreeBuilder;
+    transformTreeBuilder.build(m_displayItemList, m_displayListDiff);
+    m_transformTree = transformTreeBuilder.releaseTransformTree();
+
+    buildGraphicsLayerTree();
+
+    m_rootGraphicsLayer.setTransformTree(m_transformTree.release());
+}
+
+void DisplayListCompositingBuilder::buildGraphicsLayerTree()
+{
+    // TODO(chrishtr): implement by walking the display list and transform tree, plus additional hints, to decide layerization,
+    // including overlap testing and optimizations such as squashing.
+
+    // Also create a DisplayList for each graphics layer that is a sliced window into the DisplayItemList for the page.
+
+    // And add pixel refs.
+
+    // Trivial implementation with only one composited layer:
+    OwnPtr<DisplayList> displayList = adoptPtr(new DisplayList(m_displayItemList));
+    for (unsigned i = 0; i < m_displayItemList.displayItems().size(); i++) {
+        displayList->offsets.append(i);
+    }
+    m_rootGraphicsLayer.setDisplayList(displayList.release());
+}
+
+} // namespace blink