Update from https://crrev.com/317530

cc/resources/one_copy_tile_task_worker_pool.cc

Index: cc/resources/one_copy_tile_task_worker_pool.cc
diff --git a/cc/resources/one_copy_tile_task_worker_pool.cc b/cc/resources/one_copy_tile_task_worker_pool.cc
index cee568afa4700c5cc0e61948d7c86cc7af63b17a..e6a367af7655cd2ebe97b9f77982b4b8163dd49a 100644
--- a/cc/resources/one_copy_tile_task_worker_pool.cc
+++ b/cc/resources/one_copy_tile_task_worker_pool.cc
@@ -167,6 +167,13 @@ void OneCopyTileTaskWorkerPool::Shutdown() {
 void OneCopyTileTaskWorkerPool::ScheduleTasks(TileTaskQueue* queue) {
   TRACE_EVENT0("cc", "OneCopyTileTaskWorkerPool::ScheduleTasks");
 
+#if DCHECK_IS_ON()
+  {
+    base::AutoLock lock(lock_);
+    DCHECK(!shutdown_);
+  }
+#endif
+
   if (tasks_pending_.none())
     TRACE_EVENT_ASYNC_BEGIN0("cc", "ScheduledTasks", this);