Change CaptureSynchronizer and PointerWatcherEventRouter to support multiple CaptureClients.

ui/aura/mus/capture_synchronizer.h

Index: ui/aura/mus/capture_synchronizer.h
diff --git a/ui/aura/mus/capture_synchronizer.h b/ui/aura/mus/capture_synchronizer.h
index 87bce872168d8c50d69ab3361b1d2643d8affb9b..81e7582efada4c0c07cdaee67dad5525a770904e 100644
--- a/ui/aura/mus/capture_synchronizer.h
+++ b/ui/aura/mus/capture_synchronizer.h
@@ -22,18 +22,13 @@ 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 {
  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_; }
@@ -41,11 +36,11 @@ class CaptureSynchronizer : public WindowObserver,
   // Called when the server side wants to change capture to |window|.
   void SetCaptureFromServer(WindowMus* window);
 
- private:
   // Internal implementation for capture changes. Adds/removes observer as
   // necessary and sets |capture_window_| to |window|.
   void SetCaptureWindow(WindowMus* window);
 
+ private:
   // WindowObserver:
   void OnWindowDestroying(Window* window) override;
 
@@ -54,7 +49,6 @@ class CaptureSynchronizer : public WindowObserver,
 
   CaptureSynchronizerDelegate* delegate_;
   ui::mojom::WindowTree* window_tree_;
-  client::CaptureClient* capture_client_;
 
   // Window that currently has capture.
   WindowMus* capture_window_ = nullptr;