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

ppapi/proxy/plugin_globals.cc

Index: ppapi/proxy/plugin_globals.cc
diff --git a/ppapi/proxy/plugin_globals.cc b/ppapi/proxy/plugin_globals.cc
index ad3ad24a74e34c395151c3781345646fd9153af7..060aa71d4827536eba314941bc1c2ea6511ccfab 100644
--- a/ppapi/proxy/plugin_globals.cc
+++ b/ppapi/proxy/plugin_globals.cc
@@ -31,10 +31,10 @@ class PluginGlobals::BrowserSender : public IPC::Sender {
       : underlying_sender_(underlying_sender) {
   }
 
-  virtual ~BrowserSender() {}
+  ~BrowserSender() override {}
 
   // IPC::Sender implementation.
-  virtual bool Send(IPC::Message* msg) override {
+  bool Send(IPC::Message* msg) override {
     if (msg->is_sync()) {
       // Synchronous messages might be re-entrant, so we need to drop the lock.
       ProxyAutoUnlock unlock;