cc: Make OutputSurfaceFrame::sub_buffer_rect optional

content/browser/compositor/offscreen_browser_compositor_output_surface.cc

Index: content/browser/compositor/offscreen_browser_compositor_output_surface.cc
diff --git a/content/browser/compositor/offscreen_browser_compositor_output_surface.cc b/content/browser/compositor/offscreen_browser_compositor_output_surface.cc
index 8c7581c78d232b765dad08f9144b542e3cde64bd..bf2f87710f54171d0450e6b527ccfffbbeb99351 100644
--- a/content/browser/compositor/offscreen_browser_compositor_output_surface.cc
+++ b/content/browser/compositor/offscreen_browser_compositor_output_surface.cc
@@ -136,13 +136,12 @@ void OffscreenBrowserCompositorOutputSurface::SwapBuffers(
     cc::OutputSurfaceFrame frame) {
   gfx::Size surface_size = frame.size;
   DCHECK(surface_size == reshape_size_);
-  gfx::Rect swap_rect = frame.sub_buffer_rect;
 
   if (reflector_) {
-    if (swap_rect == gfx::Rect(surface_size))
-      reflector_->OnSourceSwapBuffers(surface_size);
+    if (frame.sub_buffer_rect)
+      reflector_->OnSourcePostSubBuffer(*frame.sub_buffer_rect, surface_size);
     else
-      reflector_->OnSourcePostSubBuffer(swap_rect, surface_size);
+      reflector_->OnSourceSwapBuffers(surface_size);
   }
 
   // TODO(oshima): sync with the reflector's SwapBuffersComplete