Update from chromium https://crrev.com/302282

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 f5496f846f50cf32d90450e0243e45943488b30d..14e218194e026d57cf300dd7a41a58ac21cb5b8b 100644
--- a/cc/trees/thread_proxy.cc
+++ b/cc/trees/thread_proxy.cc
@@ -1217,12 +1217,10 @@ void ThreadProxy::LayerTreeHostClosedOnImplThread(CompletionEvent* completion) {
   impl().scheduler = nullptr;
   impl().layer_tree_host_impl = nullptr;
   impl().weak_factory.InvalidateWeakPtrs();
-  // We need to explicitly cancel the notifier, since it isn't using weak ptrs.
-  // TODO(vmpstr): We should see if we can make it use weak ptrs and still keep
-  // the convention of having a weak ptr factory initialized last. Alternatively
-  // we should moved the notifier (and RenewTreePriority) to LTHI. See
-  // crbug.com/411972
-  impl().smoothness_priority_expiration_notifier.Cancel();
+  // We need to explicitly shutdown the notifier to destroy any weakptrs it is
+  // holding while still on the compositor thread. This also ensures any
+  // callbacks holding a ThreadProxy pointer are cancelled.
+  impl().smoothness_priority_expiration_notifier.Shutdown();
   impl().contents_texture_manager = NULL;
   completion->Signal();
 }