Add API to route end of fling messages from WebLayerTreeView to InputHandler

cc/layer_tree_host.h

Index: cc/layer_tree_host.h
diff --git a/cc/layer_tree_host.h b/cc/layer_tree_host.h
index 5c1ce68d759f4fb174708b7ee6792bbce1209f50..43da080da73b59aeb368e44ac362c53a4a846ef5 100644
--- a/cc/layer_tree_host.h
+++ b/cc/layer_tree_host.h
@@ -86,6 +86,7 @@ public:
     void willBeginFrame() { m_client->willBeginFrame(); }
     void didBeginFrame() { m_client->didBeginFrame(); }
     void updateAnimations(base::TimeTicks monotonicFrameBeginTime);
+    void mainThreadHasStoppedFlinging();
     void layout();
     void beginCommitOnImplThread(LayerTreeHostImpl*);
     void finishCommitOnImplThread(LayerTreeHostImpl*);