FrameGenerator should receive SurfaceInfo and use it in frame generation

services/ui/ws/frame_generator_delegate.h

 // 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 SERVICES_UI_WS_FRAME_GENERATOR_DELEGATE_H_
 #define SERVICES_UI_WS_FRAME_GENERATOR_DELEGATE_H_
 
 namespace ui {
 namespace ws {
 
 class FrameGeneratorDelegate {
  public:
-  // Returns the root window of the active user.
-  virtual ServerWindow* GetActiveRootWindow() = 0;
   virtual bool IsInHighContrastMode() = 0;
 
  protected:
   virtual ~FrameGeneratorDelegate() {}
 };
 
 }  // namespace ws
 }  // namespace ui
 
 #endif  // SERVICES_UI_WS_FRAME_GENERATOR_DELEGATE_H_