WIP: simplified display management in ash

ui/aura/mus/window_tree_client.h

Index: ui/aura/mus/window_tree_client.h
diff --git a/ui/aura/mus/window_tree_client.h b/ui/aura/mus/window_tree_client.h
index 6b85cc9e39becb3700cb6d3c2743116227a37bf4..06c0ae3e7d78513420a4f6f39cdc6d390c82c279 100644
--- a/ui/aura/mus/window_tree_client.h
+++ b/ui/aura/mus/window_tree_client.h
@@ -267,6 +267,11 @@ class AURA_EXPORT WindowTreeClient
                    const cc::FrameSinkId& frame_sink_id,
                    const base::Optional<cc::LocalSurfaceId>& local_surface_id);
 
+  // Called once mus acks a call to SetDisplayRoot().
+  void OnSetDisplayRootDone(
+      Id window_id,
+      const base::Optional<cc::FrameSinkId>& frame_sink_id);
+
   // Called by WmNewDisplayAdded().
   WindowTreeHostMus* WmNewDisplayAddedImpl(
       const display::Display& display,
@@ -324,7 +329,7 @@ class AURA_EXPORT WindowTreeClient
       int64_t display_id,
       Id focused_window_id,
       bool drawn,
-      const cc::FrameSinkId& frame_sink_Id,
+      const cc::FrameSinkId& frame_sink_id,
       const base::Optional<cc::LocalSurfaceId>& local_surface_id) override;
   void OnEmbeddedAppDisconnected(Id window_id) override;
   void OnUnembed(Id window_id) override;
@@ -471,6 +476,7 @@ class AURA_EXPORT WindowTreeClient
   void SetExtendedHitArea(Window* window, const gfx::Insets& hit_area) override;
   void RequestClose(Window* window) override;
   bool WaitForInitialDisplays() override;
+  WindowTreeHostMusInitParams CreateInitParamsForNewDisplay() override;
 
   // Overriden from WindowTreeHostMusDelegate:
   void OnWindowTreeHostBoundsWillChange(WindowTreeHostMus* window_tree_host,