Enforce constant size and device scale factor for surfaces

cc/surfaces/direct_compositor_frame_sink.cc

Index: cc/surfaces/direct_compositor_frame_sink.cc
diff --git a/cc/surfaces/direct_compositor_frame_sink.cc b/cc/surfaces/direct_compositor_frame_sink.cc
index 505d38ad0914acc436e7641685d1489688b9f16d..46d46c77a412823138b7a9186556fb12c7cecb47 100644
--- a/cc/surfaces/direct_compositor_frame_sink.cc
+++ b/cc/surfaces/direct_compositor_frame_sink.cc
@@ -99,15 +99,15 @@ void DirectCompositorFrameSink::SubmitCompositorFrame(CompositorFrame frame) {
             frame.metadata.begin_frame_ack.sequence_number);
 
   gfx::Size frame_size = frame.render_pass_list.back()->output_rect.size();
-  if (frame_size.IsEmpty() || frame_size != last_swap_frame_size_) {
-    delegated_local_surface_id_ = local_surface_id_allocator_.GenerateId();
+  if (!local_surface_id_.is_valid() || frame_size != last_swap_frame_size_ ||
+      frame.metadata.device_scale_factor != device_scale_factor_) {
+    local_surface_id_ = local_surface_id_allocator_.GenerateId();
     last_swap_frame_size_ = frame_size;
+    device_scale_factor_ = frame.metadata.device_scale_factor;
+    display_->SetLocalSurfaceId(local_surface_id_, device_scale_factor_);
   }
-  display_->SetLocalSurfaceId(delegated_local_surface_id_,
-                              frame.metadata.device_scale_factor);
 
-  support_->SubmitCompositorFrame(delegated_local_surface_id_,
-                                  std::move(frame));
+  DCHECK(support_->SubmitCompositorFrame(local_surface_id_, std::move(frame)));

[danakj, 2017/05/19 19:00:59]

DCHECKs are compiled out in release, so SubmitCompositorFrame will not be run at
all. You want to DCHECK a variable that it returns. Please make sure you don't
do this elsewhere too :)

[Saman Sami, 2017/05/19 19:26:46]

Oops...

 }
 
 void DirectCompositorFrameSink::DisplayOutputSurfaceLost() {