Change CaptureSynchronizer and PointerWatcherEventRouter to support multiple CaptureClients.

ui/aura/mus/capture_synchronizer.cc

Index: ui/aura/mus/capture_synchronizer.cc
diff --git a/ui/aura/mus/capture_synchronizer.cc b/ui/aura/mus/capture_synchronizer.cc
index 67dacb4e9d5672b55204f2980242e71c5ca52f0f..3e8c974ca358dbf771eeed3f580c549108753e2a 100644
--- a/ui/aura/mus/capture_synchronizer.cc
+++ b/ui/aura/mus/capture_synchronizer.cc
@@ -14,30 +14,26 @@
 namespace aura {
 
 CaptureSynchronizer::CaptureSynchronizer(CaptureSynchronizerDelegate* delegate,
-                                         ui::mojom::WindowTree* window_tree,
-                                         client::CaptureClient* capture_client)
-    : delegate_(delegate),
-      window_tree_(window_tree),
-      capture_client_(capture_client) {
-  capture_client_->AddObserver(this);
-}
+                                         ui::mojom::WindowTree* window_tree)
+    : delegate_(delegate), window_tree_(window_tree) {}
 
-CaptureSynchronizer::~CaptureSynchronizer() {
-  SetCaptureWindow(nullptr);
-  capture_client_->RemoveObserver(this);
-}
+CaptureSynchronizer::~CaptureSynchronizer() {}
 
 void CaptureSynchronizer::SetCaptureFromServer(WindowMus* window) {
   if (window == capture_window_)
     return;
 
   DCHECK(!setting_capture_);
-  // Don't immediately set |capture_client_|. It's possible the change will be
+  // Don't immediately set capture client. It's possible the change will be
   // rejected.
   base::AutoReset<bool> capture_reset(&setting_capture_, true);
   base::AutoReset<WindowMus*> window_setting_capture_to_reset(
       &window_setting_capture_to_, window);
-  capture_client_->SetCapture(window ? window->GetWindow() : nullptr);
+  client::CaptureClient* capture_client =
+      window ? client::GetCaptureClient(window->GetWindow()->GetRootWindow())
+             : client::GetCaptureClient(
+                   capture_window_->GetWindow()->GetRootWindow());
+  capture_client->SetCapture(window ? window->GetWindow() : nullptr);
 }
 
 void CaptureSynchronizer::SetCaptureWindow(WindowMus* window) {