mus: Allow embedder to intercept events.

components/mus/ws/test_utils.h

Index: components/mus/ws/test_utils.h
diff --git a/components/mus/ws/test_utils.h b/components/mus/ws/test_utils.h
index 19cb43215c0baa0fd70c3bcf27f6bb3a3beb409c..21cce2bfe80f51921f122437bb142ba0fe1bc4ba 100644
--- a/components/mus/ws/test_utils.h
+++ b/components/mus/ws/test_utils.h
@@ -81,6 +81,9 @@ class WindowTreeTestApi {
                                  mojom::EventResult::UNHANDLED);
   }
   void EnableCapture() { tree_->event_ack_id_ = 1u; }
+  void AckLastEvent(mojom::EventResult result) {
+    tree_->OnWindowInputEventAck(tree_->event_ack_id_, result);
+  }
 
   void SetEventObserver(mojom::EventMatcherPtr matcher,
                         uint32_t event_observer_id);
@@ -160,6 +163,13 @@ class WindowManagerStateTestApi {
     wms_->DispatchInputEventToWindow(target, client_id, event, accelerator);
   }
 
+  ClientSpecificId GetEventTargetClientId(ServerWindow* window,
+                                          bool in_nonclient_area) {
+    return wms_->GetEventTargetClientId(window, in_nonclient_area);
+  }
+
+  void ProcessEvent(const ui::Event& event) { wms_->ProcessEvent(event); }
+
   void OnEventAckTimeout(ClientSpecificId client_id) {
     wms_->OnEventAckTimeout(client_id);
   }