Enforce marking "override" for functions overriding Blink.

content/browser/android/in_process/context_provider_in_process.cc

Index: content/browser/android/in_process/context_provider_in_process.cc
diff --git a/content/browser/android/in_process/context_provider_in_process.cc b/content/browser/android/in_process/context_provider_in_process.cc
index 71f8010390fc96cb47e1e09449ad2680a4f860b4..cd9bd7d20dc38fc08ef8df8d966d79a11b0f6140 100644
--- a/content/browser/android/in_process/context_provider_in_process.cc
+++ b/content/browser/android/in_process/context_provider_in_process.cc
@@ -25,11 +25,11 @@ class ContextProviderInProcess::LostContextCallbackProxy
     provider_->WebContext3DImpl()->setContextLostCallback(this);
   }
 
-  virtual ~LostContextCallbackProxy() {
+  ~LostContextCallbackProxy() override {
     provider_->WebContext3DImpl()->setContextLostCallback(NULL);
   }
 
-  virtual void onContextLost() {
+  void onContextLost() override {
     provider_->OnLostContext();
   }