cc: Make OutputSurfaceFrame::sub_buffer_rect optional

cc/output/gl_renderer.cc

Index: cc/output/gl_renderer.cc
diff --git a/cc/output/gl_renderer.cc b/cc/output/gl_renderer.cc
index e03abea9585917d6c56f7bae69771a829076e3a5..b7f0dd3fea95517c944f30e6b209ae10797a621d 100644
--- a/cc/output/gl_renderer.cc
+++ b/cc/output/gl_renderer.cc
@@ -2651,10 +2651,11 @@ void GLRenderer::SwapBuffers(std::vector<ui::LatencyInfo> latency_info) {
   } else {

[danakj, 2017/02/22 00:36:57]

else if

[halliwell, 2017/02/22 14:19:27]

Done.

     // Expand the swap rect to the full surface unless it's empty, and empty
     // swap is allowed.
-    if (!swap_buffer_rect_.IsEmpty() || !allow_empty_swap_) {
+    if (swap_buffer_rect_.IsEmpty() && allow_empty_swap_) {
+      output_frame.sub_buffer_rect = swap_buffer_rect_;
+    } else {

[danakj, 2017/02/22 00:36:57]

i dont think we need this else, we clear the rect at the bottom of the method

[halliwell, 2017/02/22 14:19:27]

Done.

       swap_buffer_rect_ = gfx::Rect(surface_size);
     }
-    output_frame.sub_buffer_rect = swap_buffer_rect_;
   }
 
   swapping_overlay_resources_.push_back(std::move(pending_overlay_resources_));