Adding momentum/overscroll to views:: ScrollViews

cc/layers/layer_impl.h

Index: cc/layers/layer_impl.h
diff --git a/cc/layers/layer_impl.h b/cc/layers/layer_impl.h
index a3c621dd3577e7b350fb0880afd864e84ba66895..243822241eb7d148c26f30f8662909cd42f7ea30 100644
--- a/cc/layers/layer_impl.h
+++ b/cc/layers/layer_impl.h
@@ -315,6 +315,8 @@ class CC_EXPORT LayerImpl {
 
   void SetCurrentScrollOffset(const gfx::ScrollOffset& scroll_offset);
   gfx::ScrollOffset CurrentScrollOffset() const;
+  void SetCurrentOverscroll(const gfx::ScrollOffset& overscroll);
+  gfx::ScrollOffset CurrentOverscroll() const;
 
   gfx::ScrollOffset MaxScrollOffset() const;
   gfx::ScrollOffset ClampScrollOffsetToLimits(gfx::ScrollOffset offset) const;
@@ -324,10 +326,16 @@ class CC_EXPORT LayerImpl {
   // initial scroll
   gfx::Vector2dF ScrollBy(const gfx::Vector2dF& scroll);
 
-  void SetScrollClipLayer(int scroll_clip_layer_id);
+  // TODO(tapted): Remove this overload.
+  void SetScrollClipLayer(int scroll_clip_layer_id) {
+    SetScrollClipAndCanOverscroll(scroll_clip_layer_id, false);
+  }
+  void SetScrollClipAndCanOverscroll(int scroll_clip_layer_id,
+                                     bool can_overscroll);
   int scroll_clip_layer_id() const { return scroll_clip_layer_id_; }
   LayerImpl* scroll_clip_layer() const;
   bool scrollable() const;
+  bool can_overscroll() const { return can_overscroll_; }
 
   void set_user_scrollable_horizontal(bool scrollable);
   bool user_scrollable_horizontal() const {
@@ -518,6 +526,7 @@ class CC_EXPORT LayerImpl {
 
   bool user_scrollable_horizontal_ : 1;
   bool user_scrollable_vertical_ : 1;
+  bool can_overscroll_ : 1;
   bool should_flatten_transform_from_property_tree_ : 1;
 
   // Tracks if drawing-related properties have changed since last redraw.