Update {virtual,override} to follow C++11 style in content.

content/browser/plugin_service_impl_browsertest.cc

Index: content/browser/plugin_service_impl_browsertest.cc
diff --git a/content/browser/plugin_service_impl_browsertest.cc b/content/browser/plugin_service_impl_browsertest.cc
index b81b78cf08cfc4fb0b1cf9fd2144d0c971b38c32..e60516e67e01e8c70de1e5f0cec66b5154998e42 100644
--- a/content/browser/plugin_service_impl_browsertest.cc
+++ b/content/browser/plugin_service_impl_browsertest.cc
@@ -181,11 +181,11 @@ class MockCanceledPluginServiceClient : public PluginProcessHost::Client {
         get_resource_context_called_(false) {
   }
 
-  virtual ~MockCanceledPluginServiceClient() {}
+  ~MockCanceledPluginServiceClient() override {}
 
   // Client implementation.
   MOCK_METHOD0(ID, int());
-  virtual ResourceContext* GetResourceContext() override {
+  ResourceContext* GetResourceContext() override {
     get_resource_context_called_ = true;
     return context_;
   }