Remove unnecessary 'virtual' annotation from mojo

mojo/services/html_viewer/blink_platform_impl.cc

Index: mojo/services/html_viewer/blink_platform_impl.cc
diff --git a/mojo/services/html_viewer/blink_platform_impl.cc b/mojo/services/html_viewer/blink_platform_impl.cc
index 5c02395379308433a9201ceb371910031d945e94..7a1ee7edfb451baaedf4166048d941463d8513bc 100644
--- a/mojo/services/html_viewer/blink_platform_impl.cc
+++ b/mojo/services/html_viewer/blink_platform_impl.cc
@@ -34,10 +34,10 @@ const char kDefaultUserAgentString[] =
 class WebWaitableEventImpl : public blink::WebWaitableEvent {
  public:
   WebWaitableEventImpl() : impl_(new base::WaitableEvent(false, false)) {}
-  virtual ~WebWaitableEventImpl() {}
+  ~WebWaitableEventImpl() override {}
 
-  virtual void wait() { impl_->Wait(); }
-  virtual void signal() { impl_->Signal(); }
+  void wait() override { impl_->Wait(); }
+  void signal() override { impl_->Signal(); }
 
   base::WaitableEvent* impl() {
     return impl_.get();