Enforce marking "override" for functions overriding Blink.

content/child/service_worker/service_worker_dispatcher_unittest.cc

Index: content/child/service_worker/service_worker_dispatcher_unittest.cc
diff --git a/content/child/service_worker/service_worker_dispatcher_unittest.cc b/content/child/service_worker/service_worker_dispatcher_unittest.cc
index 5df0501c326148a3faa3dfbb91b51e537c35f918..93d9465c39de69d8ff65cfee4f6cca1f3a529822 100644
--- a/content/child/service_worker/service_worker_dispatcher_unittest.cc
+++ b/content/child/service_worker/service_worker_dispatcher_unittest.cc
@@ -116,13 +116,13 @@ class MockWebServiceWorkerProviderClientImpl
     dispatcher_->AddProviderClient(provider_id, this);
   }
 
-  ~MockWebServiceWorkerProviderClientImpl() {
+  ~MockWebServiceWorkerProviderClientImpl() override {
     dispatcher_->RemoveProviderClient(provider_id_);
   }
 
   void setController(
       blink::WebPassOwnPtr<blink::WebServiceWorker::Handle> handle,
-      bool shouldNotifyControllerChange) {
+      bool shouldNotifyControllerChange) override {
     // WebPassOwnPtr cannot be owned in Chromium, so drop the handle here.
     // The destruction releases ServiceWorkerHandleReference.
     is_set_controlled_called_ = true;