cc: Make OutputSurfaceFrame::sub_buffer_rect optional

ui/compositor/test/in_process_context_factory.cc

Index: ui/compositor/test/in_process_context_factory.cc
diff --git a/ui/compositor/test/in_process_context_factory.cc b/ui/compositor/test/in_process_context_factory.cc
index 0a5be65e9fa2348b8cd73284239acb861ecfc957..a291de0e3e76bd1f0431dc1eea3b958814d50c57 100644
--- a/ui/compositor/test/in_process_context_factory.cc
+++ b/ui/compositor/test/in_process_context_factory.cc
@@ -79,11 +79,11 @@ class DirectOutputSurface : public cc::OutputSurface {
   }
   void SwapBuffers(cc::OutputSurfaceFrame frame) override {
     DCHECK(context_provider_.get());
-    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();
     }
     gpu::gles2::GLES2Interface* gl = context_provider_->ContextGL();
     const uint64_t fence_sync = gl->InsertFenceSyncCHROMIUM();