Pinch/Zoom Infrastructure & Plumbing CL

cc/layers/layer.h

Index: cc/layers/layer.h
diff --git a/cc/layers/layer.h b/cc/layers/layer.h
index df358f2bf999a6338e49308ada1bbcfcfe94e732..033fbeca1a88944acdfb58cfc91a4dbb896febdb 100644
--- a/cc/layers/layer.h
+++ b/cc/layers/layer.h
@@ -269,11 +269,10 @@ class CC_EXPORT Layer : public base::RefCounted<Layer>,
   gfx::Vector2d scroll_offset() const { return scroll_offset_; }
   void SetScrollOffsetFromImplSide(gfx::Vector2d scroll_offset);
 
-  void SetMaxScrollOffset(gfx::Vector2d max_scroll_offset);
-  gfx::Vector2d max_scroll_offset() const { return max_scroll_offset_; }
+  gfx::Vector2d MaxScrollOffset() const;
 
-  void SetScrollable(bool scrollable);
-  bool scrollable() const { return scrollable_; }
+  void SetScrollClipLayerId(int clip_layer_id);
+  bool scrollable() const { return scroll_clip_layer_id_ != INVALID_ID; }
 
   void SetUserScrollable(bool horizontal, bool vertical);
   bool user_scrollable_horizontal() const {
@@ -565,7 +564,10 @@ class CC_EXPORT Layer : public base::RefCounted<Layer>,
   gfx::Size bounds_;
 
   gfx::Vector2d scroll_offset_;
-  gfx::Vector2d max_scroll_offset_;
+  // This variable indicates which ancestor layer (if any) whose size,
+  // transformed relative to this layer, defines the maximum scroll offset for
+  // this layer.
+  int scroll_clip_layer_id_;
   bool scrollable_ : 1;
   bool should_scroll_on_main_thread_ : 1;
   bool have_wheel_event_handlers_ : 1;