Overscroll and Elasticity for views::ScrollView

cc/input/scroll_elasticity_helper.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_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"
 #include "ui/gfx/geometry/vector2d_f.h"
 
 namespace cc {
 
 class LayerTreeHostImpl;
 
 // ScrollElasticityHelper is based on
@@ skipping 22 matching lines @@
  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
  * THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 // Interface between a LayerTreeHostImpl and the ScrollElasticityController. It
 // would be possible, in principle, for LayerTreeHostImpl to implement this
 // interface itself. This artificial boundary is introduced to reduce the amount
 // 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);
 
   virtual ~ScrollElasticityHelper() {}
 
   virtual bool IsUserScrollable() const = 0;
 
   // The amount that the view is stretched past the normal allowable bounds.
   virtual gfx::Vector2dF StretchAmount() const = 0;
   virtual void SetStretchAmount(const gfx::Vector2dF& stretch_amount) = 0;
 
   // Functions for the scrolling of the root scroll layer.
   virtual gfx::ScrollOffset ScrollOffset() const = 0;
   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;
 };
 
 }  // namespace cc
 
 #endif  // CC_INPUT_SCROLL_ELASTICITY_HELPER_H_