Change OnWindowInputEvent to use display_id to find the host and update event root_location in WS.

services/ui/ws/window_manager_state_unittest.cc

Index: services/ui/ws/window_manager_state_unittest.cc
diff --git a/services/ui/ws/window_manager_state_unittest.cc b/services/ui/ws/window_manager_state_unittest.cc
index 2b2e7e2e617af5f991dab91263922494b05dfdc1..2b9e07ec65d264aa089032d30761395fd4817e7b 100644
--- a/services/ui/ws/window_manager_state_unittest.cc
+++ b/services/ui/ws/window_manager_state_unittest.cc
@@ -384,7 +384,7 @@ TEST_F(WindowManagerStateTest, DontSendQueuedEventsToADeadTree) {
                        EF_LEFT_MOUSE_BUTTON);
   DispatchInputEventToWindow(target, press, nullptr);
   ASSERT_EQ(1u, tracker->changes()->size());
-  EXPECT_EQ("InputEvent window=1,1 event_action=1",
+  EXPECT_EQ("InputEvent window=1,1 event_action=1 event_root_location=5,5",
             ChangesToDescription1(*tracker->changes())[0]);
   tracker->changes()->clear();
   // The above is not setting TreeAwaitingInputAck.
@@ -587,6 +587,29 @@ TEST_F(WindowManagerStateTest, CursorResetOverNoTarget) {
   EXPECT_EQ(ui::mojom::Cursor::POINTER, display_test_api.last_cursor());
 }
 
+TEST_F(WindowManagerStateTest, RootLocationCoordinateConversion) {
+  TestWindowTreeClient* embed_connection = nullptr;
+  WindowTree* target_tree = nullptr;
+  ServerWindow* target = nullptr;
+  window()->SetBounds(gfx::Rect(10, 10, 100, 100));
+  CreateSecondaryTree(&embed_connection, &target_tree, &target);
+  TestWindowManager target_window_manager;
+  WindowTreeTestApi(target_tree)
+      .set_window_manager_internal(&target_window_manager);
+
+  const gfx::Point event_location(40, 50);
+  const gfx::Point event_root_location(30, 40);
+  ui::MouseEvent mouse(ui::ET_MOUSE_MOVED, event_location, event_root_location,
+                       base::TimeTicks(), 0, 0);
+  std::unique_ptr<Accelerator> accelerator = CreateAccelerator();
+  DispatchInputEventToWindow(target, mouse, accelerator.get());
+  TestChangeTracker* tracker = embed_connection->tracker();
+  ASSERT_EQ(1u, tracker->changes()->size());
+  EXPECT_EQ("InputEvent window=2,1 event_action=4 event_root_location=20,30",
+            ChangesToDescription1(*tracker->changes())[0]);
+  EXPECT_TRUE(wm_client()->tracker()->changes()->empty());
+}
+
 }  // namespace test
 }  // namespace ws
 }  // namespace ui