Implement the framework for a paint property hierarchy

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

Index: third_party/WebKit/Source/platform/graphics/paint/PaintChunkProperties.h
diff --git a/third_party/WebKit/Source/platform/graphics/paint/PaintChunkProperties.h b/third_party/WebKit/Source/platform/graphics/paint/PaintChunkProperties.h
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+// 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 PaintChunkProperties_h
+#define PaintChunkProperties_h
+
+#include "platform/graphics/paint/TransformPaintPropertyNode.h"
+
+#include <iosfwd>
+
+namespace blink {
+
+// The set of paint properties applying to a |PaintChunk|. These properties are
+// not local-only paint style parameters such as color, but instead represent
+// the hierarchy of transforms, clips, effects, etc, that apply to a contiguous
+// chunk of display items. A single DisplayItemClient can generate multiple
+// properties of the same type and this struct represents the total state of all
+// properties for a given |PaintChunk|.
+//
+// This differs from |ObjectPaintProperties| because it only stores one property
+// for each type (e.g., either transform or perspective, but not both).
+struct PaintChunkProperties {
+    // TODO(pdr): Add clip, scroll, and effect properties.
+    RefPtr<TransformPaintPropertyNode> transform;
+};
+
+// Equality is based only on the pointers and is not 'deep' which would require
+// crawling the entire property tree to compute.
+inline bool operator==(const PaintChunkProperties& a, const PaintChunkProperties& b)
+{
+    return a.transform.get() == b.transform.get();
+}
+
+inline bool operator!=(const PaintChunkProperties& a, const PaintChunkProperties& b)
+{
+    return !(a == b);
+}
+
+// Redeclared here to avoid ODR issues.
+// See platform/testing/PaintPrinters.h.
+void PrintTo(const PaintChunkProperties&, std::ostream*);
+
+} // namespace blink
+
+#endif // PaintChunkProperties_h