Changes how window manager obtains WindowTree from mus

components/mus/public/cpp/window_manager_delegate.h

Index: components/mus/public/cpp/window_manager_delegate.h
diff --git a/components/mus/public/cpp/window_manager_delegate.h b/components/mus/public/cpp/window_manager_delegate.h
index c68d9839af2f115ca001f3c6cad6a433b2217ba0..99ddf34cc4e10daae412fa917ebd078bebe9c909 100644
--- a/components/mus/public/cpp/window_manager_delegate.h
+++ b/components/mus/public/cpp/window_manager_delegate.h
@@ -18,6 +18,10 @@
 #include "components/mus/public/interfaces/window_manager_constants.mojom.h"
 #include "ui/events/mojo/event.mojom.h"
 
+namespace display {
+class Display;
+}
+
 namespace gfx {
 class Insets;
 class Rect;
@@ -96,6 +100,11 @@ class WindowManagerDelegate {
       const std::set<Window*>& client_windows,
       bool janky) = 0;
 
+  // Called when a display is added. |window| is the root of the window tree for
+  // the specified display.
+  virtual void OnWmNewDisplay(Window* window,
+                              const display::Display& display) = 0;
+
   virtual void OnAccelerator(uint32_t id, const ui::Event& event) = 0;
 
  protected: