cc: Cancel RenewTreePriorirty callback if LTHI is gone.

cc/trees/thread_proxy.cc

Index: cc/trees/thread_proxy.cc
diff --git a/cc/trees/thread_proxy.cc b/cc/trees/thread_proxy.cc
index 4a95140226db8fd2c72da44e632ebdd880bf1f5e..37d72d51d42c0d3553cd87d6e21d2acc32ffd378 100644
--- a/cc/trees/thread_proxy.cc
+++ b/cc/trees/thread_proxy.cc
@@ -1254,6 +1254,7 @@ void ThreadProxy::LayerTreeHostClosedOnImplThread(CompletionEvent* completion) {
   impl().scheduler.reset();
   impl().layer_tree_host_impl.reset();
   impl().weak_factory.InvalidateWeakPtrs();
+  impl().smoothness_priority_expiration_notifier.Cancel();

[danakj, 2014/09/08 17:33:13]

Leave a comment saying that this isn't using WeakPtr and why? (or todo if you
think it should be using that)

[vmpstr, 2014/09/08 17:42:35]

Done. Also, I filed a bug with reveman@'s suggestion and mentioned it in the
comment as a (possibly better) alternative to fix this.

   impl().contents_texture_manager = NULL;
   completion->Signal();
 }