Add OVERRIDE to media/.

media/base/async_filter_factory_base.h

Index: media/base/async_filter_factory_base.h
diff --git a/media/base/async_filter_factory_base.h b/media/base/async_filter_factory_base.h
index 0f512d159ad39e4030d218ff6ed8bdcfdfe60bb3..303bad998fcc032e0c27b6c4aa87df7339ec1233 100644
--- a/media/base/async_filter_factory_base.h
+++ b/media/base/async_filter_factory_base.h
@@ -54,7 +54,8 @@ class MEDIA_EXPORT AsyncDataSourceFactoryBase : public DataSourceFactory {
   // DataSourceFactory method.
   // Derived classes should not overload this Build() method. AllowRequests() &
   // CreateRequest() should be implemented instead.
-  virtual void Build(const std::string& url, const BuildCallback& callback);
+  virtual void Build(const std::string& url,
+                     const BuildCallback& callback) OVERRIDE;
 
   // DataSourceFactory method.
   // Clone() must be implemented by derived classes.