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

ui/aura/mus/window_tree_client_unittest.cc

Index: ui/aura/mus/window_tree_client_unittest.cc
diff --git a/ui/aura/mus/window_tree_client_unittest.cc b/ui/aura/mus/window_tree_client_unittest.cc
index 76dcf10e58846047070855359b207796cb78cc4d..85edd7b13b7bc1c3b7baeee0b95600f408eaabbc 100644
--- a/ui/aura/mus/window_tree_client_unittest.cc
+++ b/ui/aura/mus/window_tree_client_unittest.cc
@@ -22,6 +22,7 @@
 #include "ui/aura/client/focus_client.h"
 #include "ui/aura/client/transient_window_client.h"
 #include "ui/aura/mus/capture_synchronizer.h"
+#include "ui/aura/mus/mus_types.h"
 #include "ui/aura/mus/property_converter.h"
 #include "ui/aura/mus/window_mus.h"
 #include "ui/aura/mus/window_tree_client_delegate.h"
@@ -557,6 +558,43 @@ TEST_F(WindowTreeClientClientTest, InputEventBasic) {
   EXPECT_EQ(event_location_in_child, window_delegate.last_event_location());
 }
 
+TEST_F(WindowTreeClientClientTest, InputEventNoWindow) {
+  InputEventBasicTestWindowDelegate window_delegate(window_tree());
+  WindowTreeHostMus window_tree_host(window_tree_client_impl());
+  Window* top_level = window_tree_host.window();
+  const gfx::Rect bounds(0, 0, 100, 100);
+  window_tree_host.SetBoundsInPixels(bounds);
+  window_tree_host.InitHost();
+  window_tree_host.Show();
+  EXPECT_EQ(bounds, top_level->bounds());
+  EXPECT_EQ(bounds, window_tree_host.GetBoundsInPixels());
+  Window child(&window_delegate);
+  child.Init(ui::LAYER_NOT_DRAWN);
+  top_level->AddChild(&child);
+  child.SetBounds(gfx::Rect(10, 10, 100, 100));
+  child.Show();
+  EXPECT_FALSE(window_delegate.got_move());
+  EXPECT_FALSE(window_delegate.was_acked());
+  const gfx::Point event_location_in_child(20, 30);
+  std::unique_ptr<ui::Event> ui_event(
+      new ui::MouseEvent(ui::ET_MOUSE_MOVED, event_location_in_child,
+                         gfx::Point(), ui::EventTimeForNow(), ui::EF_NONE, 0));
+  window_tree_client()->OnWindowInputEvent(
+      InputEventBasicTestWindowDelegate::kEventId, kInvalidServerId,
+      window_tree_host.display_id(), ui::Event::Clone(*ui_event.get()), 0);
+  // WindowTreeClient::OnWindowInputEvent cannot find a target window with
+  // kInvalidServerId but should fall back to use the display_id to find the
+  // window_tree_host for event dispatching. child should still get the event.
+  EXPECT_TRUE(window_tree()->WasEventAcked(
+      InputEventBasicTestWindowDelegate::kEventId));
+  EXPECT_EQ(ui::mojom::EventResult::HANDLED,
+            window_tree()->GetEventResult(
+                InputEventBasicTestWindowDelegate::kEventId));
+  EXPECT_TRUE(window_delegate.got_move());
+  EXPECT_FALSE(window_delegate.was_acked());
+  EXPECT_EQ(gfx::Point(10, 20), window_delegate.last_event_location());
+}
+
 class WindowTreeClientPointerObserverTest : public WindowTreeClientClientTest {
  public:
   WindowTreeClientPointerObserverTest() {}