Enforce marking "override" for functions overriding Blink in components/.

components/scheduler/renderer/webthread_impl_for_renderer_scheduler_unittest.cc

Index: components/scheduler/renderer/webthread_impl_for_renderer_scheduler_unittest.cc
diff --git a/components/scheduler/renderer/webthread_impl_for_renderer_scheduler_unittest.cc b/components/scheduler/renderer/webthread_impl_for_renderer_scheduler_unittest.cc
index c29dbb30d251ff0bea84b1ca43536e3e90736d1b..9e3fbb2a941a92d436e41a03af6c96d23875ab7b 100644
--- a/components/scheduler/renderer/webthread_impl_for_renderer_scheduler_unittest.cc
+++ b/components/scheduler/renderer/webthread_impl_for_renderer_scheduler_unittest.cc
@@ -149,7 +149,7 @@ class ExitRunLoopTask : public blink::WebTaskRunner::Task {
  public:
   ExitRunLoopTask(base::RunLoop* run_loop) : run_loop_(run_loop) {}
 
-  virtual void run() { run_loop_->Quit(); }
+  void run() override { run_loop_->Quit(); }
 
  private:
   base::RunLoop* run_loop_;