cc: Make OutputSurfaceFrame::sub_buffer_rect optional

services/ui/surfaces/display_output_surface.cc

Index: services/ui/surfaces/display_output_surface.cc
diff --git a/services/ui/surfaces/display_output_surface.cc b/services/ui/surfaces/display_output_surface.cc
index e635a4205fa169c1d32e7ac0e1ecd5db64f7af7a..37604e770553fb265c01fceb7bd7149b56a51500 100644
--- a/services/ui/surfaces/display_output_surface.cc
+++ b/services/ui/surfaces/display_output_surface.cc
@@ -65,11 +65,11 @@ void DisplayOutputSurface::Reshape(const gfx::Size& size,
 
 void DisplayOutputSurface::SwapBuffers(cc::OutputSurfaceFrame frame) {
   DCHECK(context_provider_);
-  if (frame.sub_buffer_rect == gfx::Rect(frame.size)) {
-    context_provider_->ContextSupport()->Swap();
-  } else {
+  if (frame.sub_buffer_rect) {
     context_provider_->ContextSupport()->PartialSwapBuffers(
-        frame.sub_buffer_rect);
+        *frame.sub_buffer_rect);
+  } else {
+    context_provider_->ContextSupport()->Swap();
   }
 }