Wires up WindowTreeClient::SetDisplayRoot()

ui/aura/mus/window_manager_delegate.h

Index: ui/aura/mus/window_manager_delegate.h
diff --git a/ui/aura/mus/window_manager_delegate.h b/ui/aura/mus/window_manager_delegate.h
index 6e5b269f68e4d6c583216fe6c9a11e782f4f7d71..0441963ea68516a140edd894c9cafc734f6c6055 100644
--- a/ui/aura/mus/window_manager_delegate.h
+++ b/ui/aura/mus/window_manager_delegate.h
@@ -39,6 +39,8 @@ namespace aura {
 class Window;
 class WindowTreeHostMus;
 
+struct WindowTreeHostMusInitParams;
+
 // See the mojom with the same name for details on the functions in this
 // interface.
 class AURA_EXPORT WindowManagerClient {
@@ -66,6 +68,12 @@ class AURA_EXPORT WindowManagerClient {
   // Blocks until the initial displays have been received.
   virtual bool WaitForInitialDisplays() = 0;
 
+  // Used by the window manager to create a new display. This is only useful if
+  // the WindowTreeClient was configured not to automatically create displays
+  // (see ConnectAsWindowManager()). The caller needs to configure
+  // DisplayInitParams on the returned object.
+  virtual WindowTreeHostMusInitParams CreateInitParamsForNewDisplay() = 0;
+
  protected:
   virtual ~WindowManagerClient() {}
 };