[WIP] cc: Plumb SurfaceId from clients

content/renderer/gpu/render_widget_compositor.cc

Index: content/renderer/gpu/render_widget_compositor.cc
diff --git a/content/renderer/gpu/render_widget_compositor.cc b/content/renderer/gpu/render_widget_compositor.cc
index 513c8a66eaeb77272bc80afe5cdfead165126b32..430255726d89e99d614f708fdfb6abaefbaf494f 100644
--- a/content/renderer/gpu/render_widget_compositor.cc
+++ b/content/renderer/gpu/render_widget_compositor.cc
@@ -1125,6 +1125,10 @@ void RenderWidgetCompositor::SendCompositorProto(
   delegate_->ForwardCompositorProto(serialized);
 }
 
+uint32_t RenderWidgetCompositor::GetSurfaceClientId() const {
+  return layer_tree_host_->surface_client_id();
+}
+
 void RenderWidgetCompositor::SetSurfaceClientId(uint32_t surface_client_id) {
   layer_tree_host_->set_surface_client_id(surface_client_id);
 }