Implement the framework for the paint property hierarchy

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

Index: third_party/WebKit/Source/platform/graphics/paint/PaintArtifact.cpp
diff --git a/third_party/WebKit/Source/platform/graphics/paint/PaintArtifact.cpp b/third_party/WebKit/Source/platform/graphics/paint/PaintArtifact.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..14c70338daba8388a1c3d7f9042a704a59fc4aec
--- /dev/null
+++ b/third_party/WebKit/Source/platform/graphics/paint/PaintArtifact.cpp
@@ -0,0 +1,16 @@
+// 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.
+
+#include "config.h"
+#include "platform/graphics/paint/PaintArtifact.h"
+
+namespace blink {
+
+size_t PaintArtifact::approximateUnsharedMemoryUsage() const
+{
+    // TODO(pdr): Assert that this is only called after the merge step.
+    return sizeof(*this) + m_displayItemList.approximateUnsharedMemoryUsage();
+}
+
+} // namespace blink