Refators display related functionality into own class

components/mus/ws/display_manager_delegate.h

Index: components/mus/ws/display_manager_delegate.h
diff --git a/components/mus/ws/display_manager_delegate.h b/components/mus/ws/display_manager_delegate.h
new file mode 100644
index 0000000000000000000000000000000000000000..0af7760e60b52c19c5374d85a0893fece6c1fb72
--- /dev/null
+++ b/components/mus/ws/display_manager_delegate.h
@@ -0,0 +1,26 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_MUS_WS_DISPLAY_MANAGER_DELEGATE_H_
+#define COMPONENTS_MUS_WS_DISPLAY_MANAGER_DELEGATE_H_
+
+namespace mus {
+namespace ws {
+
+class Display;
+
+class DisplayManagerDelegate {
+ public:
+  virtual void OnWillDestroyDisplay(Display* display) = 0;
+  virtual void OnFirstDisplayReady() = 0;
+  virtual void OnNoMoreDisplays() = 0;
+
+ protected:
+  virtual ~DisplayManagerDelegate() {}
+};
+
+}  // namespace ws
+}  // namespace mus
+
+#endif  // COMPONENTS_MUS_WS_DISPLAY_MANAGER_DELEGATE_H_