WIP: simplified display management in ash

ui/aura/mus/window_tree_host_mus.h

Index: ui/aura/mus/window_tree_host_mus.h
diff --git a/ui/aura/mus/window_tree_host_mus.h b/ui/aura/mus/window_tree_host_mus.h
index b84efb4de91348693ebee5fa1641fd4bae9d2c97..a1ebe47a6d30ddb59d8582ed2f029da8599b541c 100644
--- a/ui/aura/mus/window_tree_host_mus.h
+++ b/ui/aura/mus/window_tree_host_mus.h
@@ -79,6 +79,9 @@ class AURA_EXPORT WindowTreeHostMus : public aura::WindowTreeHostPlatform {
   // PerformWindowMove().
   void CancelWindowMove();
 
+  ui::mojom::WmViewportMetricsPtr ReleaseInitialMetrics();
+  std::unique_ptr<display::Display> ReleaseInitialDisplay();
+
   // Intended only for WindowTreeClient to call.
   void set_display_id(int64_t id) { display_id_ = id; }
   int64_t display_id() const { return display_id_; }
@@ -104,6 +107,9 @@ class AURA_EXPORT WindowTreeHostMus : public aura::WindowTreeHostPlatform {
 
   std::unique_ptr<InputMethodMus> input_method_;
 
+  ui::mojom::WmViewportMetricsPtr initial_metrics_;
+  std::unique_ptr<display::Display> initial_display_;
+
   DISALLOW_COPY_AND_ASSIGN(WindowTreeHostMus);
 };