Mojo: Convert the remaining OVERRIDEs to override in mojo/.

mojo/services/native_viewport/gpu_impl.h

Index: mojo/services/native_viewport/gpu_impl.h
diff --git a/mojo/services/native_viewport/gpu_impl.h b/mojo/services/native_viewport/gpu_impl.h
index 50680616092baa81c2d2cebd398dcab4ebfe2bcc..ac0f435fb5b10f9adad55f20d0acaa5cc30198b6 100644
--- a/mojo/services/native_viewport/gpu_impl.h
+++ b/mojo/services/native_viewport/gpu_impl.h
@@ -32,10 +32,10 @@ class GpuImpl : public InterfaceImpl<Gpu> {
   virtual void CreateOnscreenGLES2Context(
       uint64_t native_viewport_id,
       SizePtr size,
-      InterfaceRequest<CommandBuffer> command_buffer_request) OVERRIDE;
+      InterfaceRequest<CommandBuffer> command_buffer_request) override;
 
   virtual void CreateOffscreenGLES2Context(
-      InterfaceRequest<CommandBuffer> command_buffer_request) OVERRIDE;
+      InterfaceRequest<CommandBuffer> command_buffer_request) override;
 
  private:
   // We need to share these across all NativeViewport instances so that contexts