Revert: Remove WindowTreeClientDelegate::GetCaptureClient() and WindowTreeClient::GetCaptureClient()

ui/views/mus/mus_client.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 UI_VIEWS_MUS_MUS_CLIENT_H_
 #define UI_VIEWS_MUS_MUS_CLIENT_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 111 matching lines @@
   friend class AuraInit;
   friend class test::MusClientTestApi;
 
   // aura::WindowTreeClientDelegate:
   void OnEmbed(
       std::unique_ptr<aura::WindowTreeHostMus> window_tree_host) override;
   void OnLostConnection(aura::WindowTreeClient* client) override;
   void OnEmbedRootDestroyed(aura::WindowTreeHostMus* window_tree_host) override;
   void OnPointerEventObserved(const ui::PointerEvent& event,
                               aura::Window* target) override;
+  aura::client::CaptureClient* GetCaptureClient() override;
   aura::PropertyConverter* GetPropertyConverter() override;
 
   // ScreenMusDelegate:
   void OnWindowManagerFrameValuesChanged() override;
   aura::Window* GetWindowAtScreenPoint(const gfx::Point& point) override;
 
   // ui:OSExchangeDataProviderFactory::Factory:
   std::unique_ptr<OSExchangeData::Provider> BuildProvider() override;
 
   static MusClient* instance_;
@@ skipping 19 matching lines @@
 
   std::unique_ptr<discardable_memory::ClientDiscardableSharedMemoryManager>
       discardable_shared_memory_manager_;
 
   DISALLOW_COPY_AND_ASSIGN(MusClient);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_MUS_MUS_CLIENT_H_