cc: Only add surface ID to embedded_surfaces if fallback does not match

cc/layers/surface_layer_impl.cc

Index: cc/layers/surface_layer_impl.cc
diff --git a/cc/layers/surface_layer_impl.cc b/cc/layers/surface_layer_impl.cc
index 7a1bfbd9795c782104a565971fac205ee98ad678..4581e556b2a5ebf87456c134e4f2d2af15a4b3bc 100644
--- a/cc/layers/surface_layer_impl.cc
+++ b/cc/layers/surface_layer_impl.cc
@@ -65,12 +65,14 @@ void SurfaceLayerImpl::PushPropertiesTo(LayerImpl* layer) {
 void SurfaceLayerImpl::AppendQuads(RenderPass* render_pass,
                                    AppendQuadsData* append_quads_data) {
   AppendRainbowDebugBorder(render_pass);
+  bool needs_synchronization =

[danakj, 2017/05/04 19:14:08]

nit: needs_fallback?

[Fady Samuel, 2017/05/04 20:03:48]

Done.

+      fallback_surface_info_.id() != primary_surface_info_.id();
   auto* primary = CreateSurfaceDrawQuad(
       render_pass, SurfaceDrawQuadType::PRIMARY, primary_surface_info_,
-      &append_quads_data->embedded_surfaces);
+      needs_synchronization ? &append_quads_data->embedded_surfaces : nullptr);

[danakj, 2017/05/04 19:14:08]

The side effects here are very unclear, with the relationship that this is
preventing embedded surfaces from adding the the surface id. Proposal: Remove
the |embedded_surfaces| from CreateSurfaceDrawQuad, and do the push_back here
directly instead.

[Fady Samuel, 2017/05/04 20:03:48]

Done.

   // Emitting a fallback SurfaceDrawQuad is unnecessary if the primary and
   // fallback surface Ids match.
-  if (primary && fallback_surface_info_.id() != primary_surface_info_.id()) {
+  if (primary && needs_synchronization) {
     primary->fallback_quad = CreateSurfaceDrawQuad(
         render_pass, SurfaceDrawQuadType::FALLBACK, fallback_surface_info_,
         nullptr /* embedded_surfaces */);