Hook ScrollElasticityController to InputHandlerProxy

cc/trees/layer_tree_host_impl.cc

Index: cc/trees/layer_tree_host_impl.cc
diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index b797c1c96963d761622d6a32b841d68ea1a25712..d807836acdd07857cc2f7fdcd0d5fb171341b572 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -65,6 +65,7 @@
 #include "cc/trees/layer_tree_host.h"
 #include "cc/trees/layer_tree_host_common.h"
 #include "cc/trees/layer_tree_impl.h"
+#include "cc/trees/layer_tree_scroll_elasticity_client.h"
 #include "cc/trees/occlusion_tracker.h"
 #include "cc/trees/single_thread_proxy.h"
 #include "cc/trees/tree_synchronizer.h"
@@ -281,6 +282,8 @@ LayerTreeHostImpl::~LayerTreeHostImpl() {
     input_handler_client_->WillShutdown();
     input_handler_client_ = NULL;
   }
+  if (scroll_elasticity_client_)
+    scroll_elasticity_client_.reset();
 
   // The layer trees must be destroyed before the layer tree host. We've
   // made a contract with our animation controllers that the registrar
@@ -394,6 +397,8 @@ bool LayerTreeHostImpl::CanDraw() const {
 void LayerTreeHostImpl::Animate(base::TimeTicks monotonic_time) {
   if (input_handler_client_)
     input_handler_client_->Animate(monotonic_time);
+  if (scroll_elasticity_client_)
+    scroll_elasticity_client_->Animate(monotonic_time);
   AnimatePageScale(monotonic_time);
   AnimateLayers(monotonic_time);
   AnimateScrollbars(monotonic_time);
@@ -450,6 +455,13 @@ LayerTreeHostImpl::CreateLatencyInfoSwapPromiseMonitor(
       new LatencyInfoSwapPromiseMonitor(latency, NULL, this));
 }
 
+ScrollElasticityControllerClient*
+LayerTreeHostImpl::GetScrollElasticityControllerClient() {
+  if (!scroll_elasticity_client_)
+    scroll_elasticity_client_.reset(new LayerTreeScrollElasticityClient(this));
+  return scroll_elasticity_client_.get();
+}
+
 void LayerTreeHostImpl::QueueSwapPromiseForMainThreadScrollUpdate(
     scoped_ptr<SwapPromise> swap_promise) {
   swap_promises_for_main_thread_scroll_update_.push_back(swap_promise.Pass());