Include transform origin in the transform tree.

public/platform/WebDisplayItemTransformTree.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 WebDisplayItemTransformTree_h
 #define WebDisplayItemTransformTree_h
 
 #include "public/platform/WebCommon.h"
 #include "public/platform/WebFloatSize.h"
 #include "public/platform/WebPrivateOwnPtr.h"
+#include "third_party/skia/include/core/SkPoint3.h"
 #include "third_party/skia/include/utils/SkMatrix44.h"
 
 namespace blink {
 
 class DisplayItemTransformTree;
 
 // Represents the hierarchy of transforms which apply to ranges of a display
 // item list and may be of interest to the compositor.
 //
 // It consists of a tree of "transform nodes", stored in a flattened
 // representation in which their order is not guaranteed. Each node has a
 // parent, relative to whom its transform should be interpreted (i.e. the
 // total transform at a node is the product of its transform and its parent's
 // total transform).
 class BLINK_PLATFORM_EXPORT WebDisplayItemTransformTree {
 public:
     enum : size_t { kInvalidIndex = static_cast<size_t>(-1) };
 
     struct TransformNode {
-        TransformNode(size_t parent, const SkMatrix44& matrix44)
+        TransformNode(size_t parent, const SkMatrix44& matrix44, const SkPoint3& origin)
             : parentNodeIndex(parent)
             , matrix(matrix44)
+            , transformOrigin(origin)
         {
         }
 
         bool isRoot() const { return parentNodeIndex == kInvalidIndex; }
 
         // Index of parent in m_nodes (kInvalidIndex for root).
         size_t parentNodeIndex;
 
         // Transformation matrix of this node, relative to its parent.
         SkMatrix44 matrix;
+
+        // Origin of the transform given by |matrix|.
+        SkPoint3 transformOrigin;
     };
 
     WebDisplayItemTransformTree();
 #if INSIDE_BLINK
     WebDisplayItemTransformTree(const WTF::PassOwnPtr<DisplayItemTransformTree>&);
 #endif
 
     ~WebDisplayItemTransformTree();
 
     // Returns the number of nodes in the transform tree.
     size_t nodeCount() const;
 
     // Returns a node in the transform tree by its index (from 0 to nodeCount() - 1).
     const TransformNode& nodeAt(size_t index) const;
 
 private:
     WebPrivateOwnPtr<const DisplayItemTransformTree> m_private;
 };
 
 } // namespace blink
 
 #endif // WebDisplayItemTransformTree_h