Slimming Paint phase 2 compositing algorithm plumbing

Source/core/compositing/DisplayListCompositingBuilder.h

Index: Source/core/compositing/DisplayListCompositingBuilder.h
diff --git a/Source/core/compositing/DisplayListCompositingBuilder.h b/Source/core/compositing/DisplayListCompositingBuilder.h
new file mode 100644
index 0000000000000000000000000000000000000000..91b86fecb89e7e038f4b8ef1bfe8ac817d36f655
--- /dev/null
+++ b/Source/core/compositing/DisplayListCompositingBuilder.h
@@ -0,0 +1,32 @@
+// Copyright 2015 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 "platform/graphics/GraphicsLayer.h"
+#include "platform/graphics/paint/DisplayItemList.h"
+#include "platform/graphics/paint/DisplayItemTransformTree.h"
+
+namespace blink {
+
+class DisplayListCompositingBuilder {
+public:
+    // TODO: SimpleLayers from the previous frame are needed as well.
+    DisplayListCompositingBuilder(const DisplayItemList& displayItemList, const DisplayListDiff& displayListDiff, GraphicsLayer& rootGraphicsLayer)

[chrishtr, 2015/08/13 17:28:31]

GraphicsLayer is probably not going to be part of the new cc API. Instead it'll
maybe be a new kind of RenderSurfaceLayerList. Let's call it a
CompositedDisplayList.

So instead I suggest you define an object of type CompositedDisplayList or
similar, and have call sites pass a pointer to it to the build() function below.
CompositedDisplayList would be:

struct CompositedDisplayList {
  Vector<SimpleLayer*>
  DisplayItemTransformTree transformTree;
  .. (other trees)

  Vector<SimpleLayerInvalidations> simpleLayerInvalidations;
}

[pdr., 2015/08/13 20:54:59]

Added CompositedDisplayList but, after implementing it, I'm not sure it actually
makes the code or api cleaner.

+        : m_displayItemList(displayItemList)
+        , m_displayListDiff(displayListDiff)
+        , m_rootGraphicsLayer(rootGraphicsLayer) {}
+
+    void build();
+
+private:
+    const DisplayItemList& m_displayItemList;
+    const DisplayListDiff& m_displayListDiff;
+    GraphicsLayer& m_rootGraphicsLayer;
+};
+
+} // namespace blink
+
+#endif // DisplayListCompositingBuilder_h