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

ppapi/shared_impl/ppb_instance_shared.h

Index: ppapi/shared_impl/ppb_instance_shared.h
diff --git a/ppapi/shared_impl/ppb_instance_shared.h b/ppapi/shared_impl/ppb_instance_shared.h
index 717adedd9e3348949fb4dcc86647a3e961149357..bcd284e4761c4f5291240baf919ef2ba7af7201e 100644
--- a/ppapi/shared_impl/ppb_instance_shared.h
+++ b/ppapi/shared_impl/ppb_instance_shared.h
@@ -15,16 +15,14 @@ namespace ppapi {
 class PPAPI_SHARED_EXPORT PPB_Instance_Shared
     : NON_EXPORTED_BASE(public thunk::PPB_Instance_API) {
  public:
-  virtual ~PPB_Instance_Shared();
+  ~PPB_Instance_Shared() override;
 
   // Implementation of some shared PPB_Instance_FunctionAPI functions.
-  virtual void Log(PP_Instance instance,
-                   PP_LogLevel log_level,
-                   PP_Var value) override;
-  virtual void LogWithSource(PP_Instance instance,
-                             PP_LogLevel log_level,
-                             PP_Var source,
-                             PP_Var value) override;
+  void Log(PP_Instance instance, PP_LogLevel log_level, PP_Var value) override;
+  void LogWithSource(PP_Instance instance,
+                     PP_LogLevel log_level,
+                     PP_Var source,
+                     PP_Var value) override;
 
   // Error checks the given resquest to Request[Filtering]InputEvents. Returns
   // PP_OK if the given classes are all valid, PP_ERROR_NOTSUPPORTED if not.