Change CaptureSynchronizer and PointerWatcherEventRouter to support multiple CaptureClients.

ui/aura/mus/window_tree_client.cc

Index: ui/aura/mus/window_tree_client.cc
diff --git a/ui/aura/mus/window_tree_client.cc b/ui/aura/mus/window_tree_client.cc
index 743f1a08ac47ea684516d8dce76b1a5e57924d75..00012d247c442238ebfb4f8e21c1e073b29fdb1b 100644
--- a/ui/aura/mus/window_tree_client.cc
+++ b/ui/aura/mus/window_tree_client.cc
@@ -22,6 +22,7 @@
 #include "services/ui/public/interfaces/window_manager.mojom.h"
 #include "services/ui/public/interfaces/window_manager_window_tree_factory.mojom.h"
 #include "ui/aura/client/aura_constants.h"
+#include "ui/aura/client/capture_client.h"
 #include "ui/aura/client/drag_drop_client.h"
 #include "ui/aura/client/transient_window_client.h"
 #include "ui/aura/env.h"
@@ -467,8 +468,7 @@ void WindowTreeClient::WindowTreeConnectionEstablished(
   tree_ = window_tree;
 
   drag_drop_controller_ = base::MakeUnique<DragDropControllerMus>(this, tree_);
-  capture_synchronizer_ =
-      base::MakeUnique<CaptureSynchronizer>(this, tree_, GetCaptureClient());
+  capture_synchronizer_ = base::MakeUnique<CaptureSynchronizer>(this, tree_);
   focus_synchronizer_ = base::MakeUnique<FocusSynchronizer>(this, tree_);
 }
 
@@ -829,6 +829,17 @@ void WindowTreeClient::CancelWindowMove(Window* window) {
   tree_->CancelWindowMove(WindowMus::Get(window)->server_id());
 }
 
+void WindowTreeClient::OnCaptureClientSet(
+    client::CaptureClient* capture_client) {
+  capture_client->AddObserver(capture_synchronizer_.get());
+}
+
+void WindowTreeClient::OnCaptureClientUnset(
+    client::CaptureClient* capture_client) {
+  capture_synchronizer_->SetCaptureWindow(nullptr);
+  capture_client->RemoveObserver(capture_synchronizer_.get());

[sadrul, 2017/01/27 01:06:53]

Can this be replaced by adding functions on CaptureSynchronizer instead? e.g. in
OnCaptureClientSet() above:

  capture_synchronizer_->AttachToCaptureClient(capture_client);

and here:

  capture_synchronizer_->DetachFromCaptureClient(capture_client);

The CaptureSynchronizer can take care of updating its internal state, instead of
having to do that from here (the call to SetCaptureWindow(nullptr))

+}
+
 void WindowTreeClient::AddObserver(WindowTreeClientObserver* observer) {
   observers_.AddObserver(observer);
 }