WIP: Propagate SurfaceID up window tree hierarchy

services/ui/ws/platform_display.cc

Index: services/ui/ws/platform_display.cc
diff --git a/services/ui/ws/platform_display.cc b/services/ui/ws/platform_display.cc
index 6a082d23af54525b8fe78086e153d92950b71802..3c6494f8af904ef91d4f5f0e1d129a5a3c0b2fd2 100644
--- a/services/ui/ws/platform_display.cc
+++ b/services/ui/ws/platform_display.cc
@@ -13,8 +13,8 @@
 #include "services/shell/public/cpp/connection.h"
 #include "services/shell/public/cpp/connector.h"
 #include "services/ui/display/platform_screen.h"
+#include "services/ui/surfaces/compositor_frame_sink.h"
 #include "services/ui/surfaces/display_compositor.h"
-#include "services/ui/surfaces/surfaces_state.h"
 #include "services/ui/ws/platform_display_factory.h"
 #include "services/ui/ws/platform_display_init_params.h"
 #include "services/ui/ws/server_window.h"
@@ -59,7 +59,8 @@ DefaultPlatformDisplay::DefaultPlatformDisplay(
 #if !defined(OS_ANDROID)
       cursor_loader_(ui::CursorLoader::Create()),
 #endif
-      frame_generator_(new FrameGenerator(this, init_params.surfaces_state)) {
+      frame_generator_(
+          new FrameGenerator(this, init_params.display_compositor)) {
   metrics_.bounds = init_params.display_bounds;
 }
 
@@ -285,6 +286,10 @@ void DefaultPlatformDisplay::RequestCopyOfOutput(
   frame_generator_->RequestCopyOfOutput(std::move(output_request));
 }
 
+ServerWindow* DefaultPlatformDisplay::GetActiveRootWindow() {
+  return delegate_->GetActiveRootWindow();
+}
+
 ServerWindow* DefaultPlatformDisplay::GetRootWindow() {
   return delegate_->GetRootWindow();
 }