Change CaptureSynchronizer and PointerWatcherEventRouter to support multiple CaptureClients.

ui/aura/mus/capture_synchronizer.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_AURA_MUS_CAPTURE_SYNCHRONIZER_H_
 #define UI_AURA_MUS_CAPTURE_SYNCHRONIZER_H_
 
 #include <stdint.h>
 
 #include "base/macros.h"
@@ skipping 10 matching lines @@
 namespace aura {
 class CaptureSynchronizerDelegate;
 class WindowMus;
 
 namespace client {
 class CaptureClient;
 }
 
 // CaptureSynchronizer is resonsible for keeping capture in sync between aura
 // and the mus server.
-class CaptureSynchronizer : public WindowObserver,
-                            public client::CaptureClientObserver {
+class AURA_EXPORT CaptureSynchronizer : public WindowObserver,
+                                        public client::CaptureClientObserver {
  public:
   CaptureSynchronizer(CaptureSynchronizerDelegate* delegate,
-                      ui::mojom::WindowTree* window_tree,
-                      client::CaptureClient* capture_client);
+                      ui::mojom::WindowTree* window_tree);
   ~CaptureSynchronizer() override;
 
   WindowMus* capture_window() { return capture_window_; }
 
   // Called when the server side wants to change capture to |window|.
   void SetCaptureFromServer(WindowMus* window);
 
+  // Called when the |capture_client| has been set or will be unset.
+  void AttachToCaptureClient(client::CaptureClient* capture_client);
+  void DetachFromCaptureClient(client::CaptureClient* capture_client);
+
  private:
   // Internal implementation for capture changes. Adds/removes observer as
   // necessary and sets |capture_window_| to |window|.
   void SetCaptureWindow(WindowMus* window);
 
   // WindowObserver:
   void OnWindowDestroying(Window* window) override;
 
   // client::CaptureClientObserver:
   void OnCaptureChanged(Window* lost_capture, Window* gained_capture) override;
 
   CaptureSynchronizerDelegate* delegate_;
   ui::mojom::WindowTree* window_tree_;
-  client::CaptureClient* capture_client_;
 
   // Window that currently has capture.
   WindowMus* capture_window_ = nullptr;
 
   // Used when setting capture from the server to avoid setting capture back
   // on the server. If |setting_capture_| is true SetCaptureFromServer() was
   // called and |window_setting_capture_to_| is the window capture is being
   // set on.
   bool setting_capture_ = false;
   WindowMus* window_setting_capture_to_ = nullptr;
 
   DISALLOW_COPY_AND_ASSIGN(CaptureSynchronizer);
 };
 
 }  // namespace aura
 
 #endif  // UI_AURA_MUS_CAPTURE_SYNCHRONIZER_H_