Nit: Remove superfluous global namespace prefix

Bug: 901345
Change-Id: I3fb2bcdab9a61fc818da6a4cc6439635f9421b31
Reviewed-on: https://chromium-review.googlesource.com/c/1346834Reviewed-by: Gabriel Charette <gab@chromium.org>
Commit-Queue: Gabriel Charette <gab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610220}

base/task/sequence_manager/thread_controller_with_message_pump_impl.h

@@ -148,7 +148,7 @@ class BASE_EXPORT ThreadControllerWithMessagePumpImpl
       GUARDED_BY(task_runner_lock_);
 
   // OperationsController will only be started after |pump_| is set.
-  ::base::internal::OperationsController operations_controller_;
+  base::internal::OperationsController operations_controller_;
 
   // Can only be set once (just before calling
   // operations_controller_.StartAcceptingOperations()). After that only read