mus: Add EventObserver to allow passively listening to UI events

components/mus/ws/test_utils.cc

Index: components/mus/ws/test_utils.cc
diff --git a/components/mus/ws/test_utils.cc b/components/mus/ws/test_utils.cc
index d1563da167dcf0f6935e49f6db02d018550994da..a8490ede9fbead891f994d26c86329b45bc346c7 100644
--- a/components/mus/ws/test_utils.cc
+++ b/components/mus/ws/test_utils.cc
@@ -109,6 +109,10 @@ PlatformDisplay* TestPlatformDisplayFactory::CreatePlatformDisplay() {
 WindowTreeTestApi::WindowTreeTestApi(WindowTree* tree) : tree_(tree) {}
 WindowTreeTestApi::~WindowTreeTestApi() {}
 
+void WindowTreeTestApi::SetEventObserver(mojom::EventMatcherPtr matcher) {
+  tree_->SetEventObserver(std::move(matcher));
+}
+
 // DisplayTestApi  ------------------------------------------------------------
 
 DisplayTestApi::DisplayTestApi(Display* display) : display_(display) {}
@@ -255,8 +259,13 @@ void TestWindowTreeClient::OnWindowSharedPropertyChanged(
 
 void TestWindowTreeClient::OnWindowInputEvent(uint32_t event_id,
                                               uint32_t window,
-                                              mojom::EventPtr event) {
-  tracker_.OnWindowInputEvent(window, std::move(event));
+                                              mojom::EventPtr event,
+                                              bool matched_observer) {
+  tracker_.OnWindowInputEvent(window, std::move(event), matched_observer);
+}
+
+void TestWindowTreeClient::OnEventObserved(mojom::EventPtr event) {
+  tracker_.OnEventObserved(std::move(event));
 }
 
 void TestWindowTreeClient::OnWindowFocused(uint32_t focused_window_id) {