Notify main-thread of top controls state changes

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 f51c61ac2fd55faa576b0ea64255d26d90705fd5..9f7865e2da50920788c0594716ba0fbf5a1bb8cd 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -935,6 +935,7 @@ DrawResult LayerTreeHostImpl::CalculateRenderPasses(
 }
 
 void LayerTreeHostImpl::MainThreadHasStoppedFlinging() {
+  ScrollEnd();

[aelias_OOO_until_Jul13, 2015/02/12 00:45:29]

Not sure we want the "ClearCurrentlyScrollingLayer();" behavior of ScrollEnd. 
There could also be other things added there later that are also incompatible
with main-thread flings -- there's a strong expectation that ScrollEnd matches
ScrollBegin.  I'd suggest adding a new method
TopControlsManager::MainThreadHasStoppedFlinging that just calls
StartAnimationIfNecessary.

[majidvp, 2015/02/12 13:51:48]

Acknowledged.

   if (input_handler_client_)
     input_handler_client_->MainThreadHasStoppedFlinging();
 }