mus: Implement Window Server Capture

components/mus/test_change_tracker.h

Index: components/mus/test_change_tracker.h
diff --git a/components/mus/test_change_tracker.h b/components/mus/test_change_tracker.h
index 358a4645a41dbae35360f34f0552cb3645ef2a5f..eb8607129730127d1b4f51aadbe5c217bebdcb9e 100644
--- a/components/mus/test_change_tracker.h
+++ b/components/mus/test_change_tracker.h
@@ -20,6 +20,7 @@ enum ChangeType {
   CHANGE_TYPE_EMBED,
   CHANGE_TYPE_EMBEDDED_APP_DISCONNECTED,
   CHANGE_TYPE_UNEMBED,
+  CHANGE_TYPE_LOST_CAPTURE,
   // TODO(sky): nuke NODE.
   CHANGE_TYPE_NODE_BOUNDS_CHANGED,
   CHANGE_TYPE_NODE_VIEWPORT_METRICS_CHANGED,
@@ -120,6 +121,7 @@ class TestChangeTracker {
   void OnEmbed(ConnectionSpecificId connection_id, mojo::ViewDataPtr root);
   void OnEmbeddedAppDisconnected(Id view_id);
   void OnUnembed();
+  void OnLostCapture(Id view_id);
   void OnViewBoundsChanged(Id view_id,
                            mojo::RectPtr old_bounds,
                            mojo::RectPtr new_bounds);