mus: Add EventObserver to allow passively listening to UI events

components/mus/ws/window_tree_unittest.cc

Index: components/mus/ws/window_tree_unittest.cc
diff --git a/components/mus/ws/window_tree_unittest.cc b/components/mus/ws/window_tree_unittest.cc
index 6a191b4f838fa5f3abab95d371a95689369a25ed..3e7d486e1215a451f25b2e5ce9ccc7ebedc97544 100644
--- a/components/mus/ws/window_tree_unittest.cc
+++ b/components/mus/ws/window_tree_unittest.cc
@@ -89,6 +89,13 @@ ServerWindow* GetCaptureWindow(Display* display) {
   return display->GetActiveWindowManagerState()->capture_window();
 }
 
+mojom::EventMatcherPtr CreateEventMatcher(mojom::EventType type) {
+  mojom::EventMatcherPtr matcher = mojom::EventMatcher::New();
+  matcher->type_matcher = mojom::EventTypeMatcher::New();
+  matcher->type_matcher->type = type;
+  return matcher;
+}
+
 }  // namespace
 
 // -----------------------------------------------------------------------------
@@ -170,6 +177,7 @@ class WindowTreeTest : public testing::Test {
     display_binding_ = new TestDisplayBinding(display_, window_server_.get());
     display_->Init(base::WrapUnique(display_binding_));
     wm_client_ = delegate_.last_client();
+    wm_client_->tracker()->changes()->clear();
   }
 
  protected:
@@ -208,6 +216,7 @@ void WindowTreeTest::SetupEventTargeting(TestWindowTreeClient** out_client,
   WindowTree* tree1 = window_server()->GetTreeWithRoot(embed_window);
   ASSERT_TRUE(tree1 != nullptr);
   ASSERT_NE(tree1, wm_tree());
+  WindowTreeTestApi(tree1).set_user_id(wm_tree()->user_id());
 
   embed_window->SetBounds(gfx::Rect(0, 0, 50, 50));
 
@@ -334,6 +343,113 @@ TEST_F(WindowTreeTest, BasicInputEventTarget) {
             ChangesToDescription1(*embed_connection->tracker()->changes())[1]);
 }
 
+// Tests that a client can observe events outside its bounds.
+TEST_F(WindowTreeTest, SetEventObserver) {
+  // Create an embedded client.
+  TestWindowTreeClient* client = nullptr;
+  WindowTree* tree = nullptr;
+  ServerWindow* window = nullptr;
+  EXPECT_NO_FATAL_FAILURE(SetupEventTargeting(&client, &tree, &window));
+
+  // Create an event outside the bounds of the client.
+  ui::PointerEvent pointer_down = CreatePointerDownEvent(5, 5);
+
+  // Events are not observed before setting an observer.
+  DispatchEventAndAckImmediately(pointer_down);
+  ASSERT_EQ(0u, client->tracker()->changes()->size());
+
+  // Create an observer for pointer-down events.
+  WindowTreeTestApi(tree).SetEventObserver(
+      CreateEventMatcher(mojom::EventType::POINTER_DOWN), 111u);
+
+  // Pointer-down events are sent to the client.
+  DispatchEventAndAckImmediately(pointer_down);
+  ASSERT_EQ(1u, client->tracker()->changes()->size());
+  EXPECT_EQ("EventObserved event_action=4 event_observer_id=111",
+            ChangesToDescription1(*client->tracker()->changes())[0]);
+  client->tracker()->changes()->clear();
+
+  // Clearing the observer stops sending events to the client.
+  WindowTreeTestApi(tree).SetEventObserver(nullptr, 0u);
+  DispatchEventAndAckImmediately(pointer_down);
+  ASSERT_EQ(0u, client->tracker()->changes()->size());
+}
+
+// Tests that a client using an event observer does not receive events that
+// don't match the EventMatcher spec.
+TEST_F(WindowTreeTest, SetEventObserverNonMatching) {
+  // Create an embedded client.
+  TestWindowTreeClient* client = nullptr;
+  WindowTree* tree = nullptr;
+  ServerWindow* window = nullptr;
+  EXPECT_NO_FATAL_FAILURE(SetupEventTargeting(&client, &tree, &window));
+
+  // Create an observer for pointer-down events.
+  WindowTreeTestApi(tree).SetEventObserver(
+      CreateEventMatcher(mojom::EventType::POINTER_DOWN), 111u);
+
+  // Pointer-up events are not sent to the client, since they don't match.
+  DispatchEventAndAckImmediately(CreatePointerUpEvent(5, 5));
+  ASSERT_EQ(0u, client->tracker()->changes()->size());
+}
+
+// Tests that an event that both hits a client window and matches an event
+// observer is sent only once to the client.
+TEST_F(WindowTreeTest, SetEventObserverSendsOnce) {
+  // Create an embedded client.
+  TestWindowTreeClient* client = nullptr;
+  WindowTree* tree = nullptr;
+  ServerWindow* window = nullptr;
+  EXPECT_NO_FATAL_FAILURE(SetupEventTargeting(&client, &tree, &window));
+
+  // Create an observer for pointer-up events (which do not cause focus
+  // changes).
+  WindowTreeTestApi(tree).SetEventObserver(
+      CreateEventMatcher(mojom::EventType::POINTER_UP), 111u);
+
+  // Create an event inside the bounds of the client.
+  ui::PointerEvent pointer_up = CreatePointerUpEvent(25, 25);
+
+  // The event is dispatched once, with a flag set that it matched the event
+  // observer.
+  DispatchEventAndAckImmediately(pointer_up);
+  ASSERT_EQ(1u, client->tracker()->changes()->size());
+  EXPECT_EQ("InputEvent window=2,1 event_action=6 event_observer_id=111",
+            SingleChangeToDescription(*client->tracker()->changes()));
+}
+
+// Tests that events generated by user A are not observed by event observers for
+// user B.
+TEST_F(WindowTreeTest, SetEventObserverWrongUser) {
+  // Embed a window tree belonging to a different user.
+  TestWindowTreeBinding* other_binding;
+  WindowTree* other_tree = CreateNewTree("other_user", &other_binding);
+  other_binding->client()->tracker()->changes()->clear();
+
+  // Set event observers on both the wm tree and the other user's tree.
+  WindowTreeTestApi(wm_tree()).SetEventObserver(
+      CreateEventMatcher(mojom::EventType::POINTER_UP), 111u);
+  WindowTreeTestApi(other_tree)
+      .SetEventObserver(CreateEventMatcher(mojom::EventType::POINTER_UP), 222u);
+
+  // An event is observed by the wm tree, but not by the other user's tree.
+  DispatchEventAndAckImmediately(CreatePointerUpEvent(5, 5));
+  ASSERT_EQ(1u, wm_client()->tracker()->changes()->size());
+  EXPECT_EQ("InputEvent window=0,3 event_action=6 event_observer_id=111",
+            SingleChangeToDescription(*wm_client()->tracker()->changes()));
+  ASSERT_EQ(0u, other_binding->client()->tracker()->changes()->size());
+}
+
+// Tests that an event observer can receive events that have no target window.
+TEST_F(WindowTreeTest, SetEventObserverNoTarget) {
+  WindowTreeTestApi(wm_tree()).SetEventObserver(
+      CreateEventMatcher(mojom::EventType::KEY_RELEASED), 111u);
+  ui::KeyEvent key(ui::ET_KEY_RELEASED, ui::VKEY_A, ui::EF_NONE);
+  DispatchEventAndAckImmediately(key);
+  EXPECT_EQ("EventObserved event_action=2 event_observer_id=111",
+            SingleChangeToDescription(*wm_client()->tracker()->changes()));
+}
+
 TEST_F(WindowTreeTest, CursorChangesWhenMouseOverWindowAndWindowSetsCursor) {
   TestWindowTreeClient* embed_connection = nullptr;
   WindowTree* tree = nullptr;