Overscroll and Elasticity for views::ScrollView

cc/input/scroll_elasticity_helper.h

Index: cc/input/scroll_elasticity_helper.h
diff --git a/cc/input/scroll_elasticity_helper.h b/cc/input/scroll_elasticity_helper.h
index 3ad28fb2cbd6cfaabd1ffa9d59f5e64d9175c535..766c5dfbc707f54e7ed336e75006d6feb5aff4f3 100644
--- a/cc/input/scroll_elasticity_helper.h
+++ b/cc/input/scroll_elasticity_helper.h
@@ -5,6 +5,9 @@
 #ifndef CC_INPUT_SCROLL_ELASTICITY_HELPER_H_
 #define CC_INPUT_SCROLL_ELASTICITY_HELPER_H_
 
+#include <memory>
+
+#include "base/memory/weak_ptr.h"
 #include "base/time/time.h"
 #include "cc/base/cc_export.h"
 #include "ui/gfx/geometry/scroll_offset.h"
@@ -47,6 +50,9 @@ class LayerTreeHostImpl;
 // of logic and state held directly inside LayerTreeHostImpl.
 class CC_EXPORT ScrollElasticityHelper {
  public:
+  static std::unique_ptr<ScrollElasticityHelper> CreateForLayer(
+      int layer_scroll_layer_id,
+      LayerTreeHostImpl* layer_tree_host_impl);
   static ScrollElasticityHelper* CreateForLayerTreeHostImpl(
       LayerTreeHostImpl* layer_tree_host_impl);
 
@@ -63,6 +69,8 @@ class CC_EXPORT ScrollElasticityHelper {
   virtual gfx::ScrollOffset MaxScrollOffset() const = 0;
   virtual void ScrollBy(const gfx::Vector2dF& delta) = 0;
 
+  virtual base::WeakPtr<ScrollElasticityHelper> GetWeakPtr() = 0;
+
   // Requests that another frame happens for the controller to continue ticking
   // animations.
   virtual void RequestOneBeginFrame() = 0;