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

Source/core/compositing/DisplayListCompositingBuilder.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 DisplayListCompositingBuilder_h
+#define DisplayListCompositingBuilder_h
+
+#include "core/CoreExport.h"
+#include "platform/graphics/GraphicsLayer.h"
+#include "platform/graphics/paint/DisplayItemList.h"
+#include "platform/graphics/paint/DisplayItemTransformTree.h"
+#include "public/platform/WebDisplayList.h"
+
+namespace blink {
+
+class DisplayListCompositingBuilder {
+public:
+    // The arguments to this method are the current frame's display list, the diff from the previous frame's display list, the graphics layer at the root of the
+    // tree for this web view, and the property trees for the previous frame.
+    DisplayListCompositingBuilder(const DisplayItemList& displayList, const WebDisplayListDiff& displayListDiff, GraphicsLayer& rootGraphicsLayer)
+        : m_displayList(displayList), m_displayListDiff(displayListDiff)
+        , m_rootGraphicsLayer(rootGraphicsLayer)
+    { }
+
+    // The effect of this method is an updated graphics layer tree (still rooted at |rootGraphicsLayer|), and property trees (call releaseTransformTre()).
+    // For graphics layers which are preserved across the update, raster invalidations are registered on them (via setNeedsDisplayInRect or setNeedsDisplay).
+    void build();
+
+private:
+    void buildGraphicsLayerTree();
+
+    const DisplayItemList& m_displayList;
+    const WebDisplayListDiff& m_displayListDiff;
+    GraphicsLayer& m_rootGraphicsLayer;
+    OwnPtr<DisplayItemTransformTree> m_transformTree;
+};
+
+} // namespace blink
+
+#endif // DisplayListCompositingBuilder_h