Implement the framework for the paint property hierarchy

third_party/WebKit/Source/platform/graphics/paint/PaintArtifact.h

+// 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 PaintArtifact_h
+#define PaintArtifact_h
+
+#include "platform/PlatformExport.h"
+#include "platform/graphics/paint/DisplayItemList.h"
+#include "platform/graphics/paint/PaintChunk.h"
+#include "wtf/PassOwnPtr.h"
+#include "wtf/Vector.h"
+
+namespace blink {
+
+// The output of painting, consisting of a list of display items and the paint
+// chunks that demarcate potential compositing layers.
+//
+// In slimming paint v1, only the display item list is used.
+class PLATFORM_EXPORT PaintArtifact {
+    WTF_MAKE_NONCOPYABLE(PaintArtifact);
+    WTF_MAKE_FAST_ALLOCATED(PaintArtifact);
+public:
+    static PassOwnPtr<PaintArtifact> create()
+    {
+        return adoptPtr(new PaintArtifact());
+    }
+
+    DisplayItemList& displayItemList() { return m_displayItemList; }
+
+    // Returns the approximate memory usage, excluding memory likely to be
+    // shared with the embedder after copying to WebDisplayItemList.
+    size_t approximateUnsharedMemoryUsage() const;
+
+private:
+    PaintArtifact() { }
+
+    // TODO(pdr): Extract out the display item list merge step into this class
+    // and let the display item list truly be a list of display items.
+    DisplayItemList m_displayItemList;

[jbroman, 2015/10/07 15:22:22]

Hmm. We already have a true "list of display items", called DisplayItems (in
DisplayItemList.h). I'd suggest a refactor more like:

PaintArtifact: single copy of the data (list of display items + paint chunks +
whatever else is needed)
PaintArtifactBuilder: responsible for building a new PaintArtifact based on
commands from core/paint/ and a pointer to the previous paint artifact (merge
algorithm goes here)

WDYT? I'm happy to discuss in more detail in today's meeting.

+    Vector<PaintChunk> m_paintChunks;
+};
+
+} // namespace blink
+
+#endif // PaintArtifact_h