cc: Fix property tree position updates when rebuilding is skipped

cc/trees/property_tree.h

 // Copyright 2014 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 CC_TREES_PROPERTY_TREE_H_
 #define CC_TREES_PROPERTY_TREE_H_
 
 #include <vector>
 
 #include "base/basictypes.h"
@@ skipping 42 matching lines @@
   gfx::Transform from_target;
 
   gfx::Transform to_screen;
   gfx::Transform from_screen;
 
   int target_id;
   // This id is used for all content that draws into a render surface associated
   // with this transform node.
   int content_target_id;
 
+  // This is the node with respect to which source_offset is defined. This will
+  // not be needed once layerization moves to cc, but is needed in order to
+  // efficiently update the transform tree for changes to position in the layer
+  // tree.
+  int source_node_id;
+
   // TODO(vollick): will be moved when accelerated effects are implemented.
   bool needs_local_transform_update;
 
   bool is_invertible;
   bool ancestors_are_invertible;
 
   bool is_animated;
   bool to_screen_is_animated;
 
   // Flattening, when needed, is only applied to a node's inherited transform,
@@ skipping 18 matching lines @@
 
   // TODO(vollick): will be moved when accelerated effects are implemented.
   gfx::Vector2dF scroll_offset;
 
   // We scroll snap where possible, but this has an effect on scroll
   // compensation: the snap is yet more scrolling that must be compensated for.
   // This value stores the snapped amount for this purpose.
   gfx::Vector2dF scroll_snap;
 
   // TODO(vollick): will be moved when accelerated effects are implemented.
-  gfx::Vector2dF parent_offset;
+  gfx::Vector2dF source_offset;
 
   void set_to_parent(const gfx::Transform& transform) {
     to_parent = transform;
     is_invertible = to_parent.IsInvertible();
   }
 
   void update_pre_local_transform(const gfx::Point3F& transform_origin);
 
   void update_post_local_transform(const gfx::PointF& position,
                                    const gfx::Point3F& transform_origin);
@@ skipping 119 matching lines @@
 
   TransformTree transform_tree;
   OpacityTree opacity_tree;
   ClipTree clip_tree;
   bool needs_rebuild;
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_PROPERTY_TREE_H_