Overscroll and Elasticity for views::ScrollView

cc/layers/layer.h

Index: cc/layers/layer.h
diff --git a/cc/layers/layer.h b/cc/layers/layer.h
index dd0464e4f79872b96d577d79fa02e425e7b34ddc..4f771b9b1ddb3a553cb0dc4c5ccd744cded11ca1 100644
--- a/cc/layers/layer.h
+++ b/cc/layers/layer.h
@@ -234,10 +234,17 @@ class CC_EXPORT Layer : public base::RefCounted<Layer> {
   void SetScrollOffset(const gfx::ScrollOffset& scroll_offset);
 
   gfx::ScrollOffset scroll_offset() const { return inputs_.scroll_offset; }
-  void SetScrollOffsetFromImplSide(const gfx::ScrollOffset& scroll_offset);
+  void SetScrollOffsetFromImplSide(const gfx::ScrollOffset& scroll_offset,
+                                   gfx::Vector2dF* overscroll_delta);
+
+  // TODO(tapted): Remove this overload.
+  void SetScrollClipLayerId(int clip_layer_id) {
+    SetScrollClipAndCanOverscroll(clip_layer_id, false);
+  }
+  void SetScrollClipAndCanOverscroll(int clip_layer_id, bool can_overscroll);
 
-  void SetScrollClipLayerId(int clip_layer_id);
   bool scrollable() const { return inputs_.scroll_clip_layer_id != INVALID_ID; }
+  gfx::ScrollOffset overscroll() const { return inputs_.overscroll; }
   Layer* scroll_clip_layer() const;
 
   void SetUserScrollable(bool horizontal, bool vertical);
@@ -280,6 +287,7 @@ class CC_EXPORT Layer : public base::RefCounted<Layer> {
   gfx::ScrollOffset CurrentScrollOffset() const {
     return inputs_.scroll_offset;
   }
+  gfx::ScrollOffset CurrentOverscroll() const { return inputs_.overscroll; }
 
   void SetDoubleSided(bool double_sided);
   bool double_sided() const { return inputs_.double_sided; }
@@ -661,6 +669,7 @@ class CC_EXPORT Layer : public base::RefCounted<Layer> {
     gfx::PointF filters_origin;
 
     gfx::ScrollOffset scroll_offset;
+    gfx::ScrollOffset overscroll;
 
     // This variable indicates which ancestor layer (if any) whose size,
     // transformed relative to this layer, defines the maximum scroll offset
@@ -668,6 +677,7 @@ class CC_EXPORT Layer : public base::RefCounted<Layer> {
     int scroll_clip_layer_id;
     bool user_scrollable_horizontal : 1;
     bool user_scrollable_vertical : 1;
+    bool can_overscroll : 1;
 
     uint32_t main_thread_scrolling_reasons;
     Region non_fast_scrollable_region;