IME for Mus: Send ack for key events after IME driver processes the event.

ui/views/mus/window_tree_host_mus.cc

Index: ui/views/mus/window_tree_host_mus.cc
diff --git a/ui/views/mus/window_tree_host_mus.cc b/ui/views/mus/window_tree_host_mus.cc
index caed894310e48e65017d0b3d2b56882ca5b1a22f..5b467f7e0d786fa31557fac3e38840238c1fd450 100644
--- a/ui/views/mus/window_tree_host_mus.cc
+++ b/ui/views/mus/window_tree_host_mus.cc
@@ -53,9 +53,6 @@ WindowTreeHostMus::WindowTreeHostMus(NativeWidgetMus* native_widget,
   // TODO(sky): we need to transform for device scale though.
   dispatcher()->set_transform_events(false);
   compositor()->SetHostHasTransparentBackground(true);
-
-  input_method_ = base::MakeUnique<InputMethodMus>(this, window);
-  SetSharedInputMethod(input_method_.get());
 }
 
 WindowTreeHostMus::~WindowTreeHostMus() {
@@ -63,15 +60,9 @@ WindowTreeHostMus::~WindowTreeHostMus() {
   DestroyDispatcher();
 }
 
-void WindowTreeHostMus::InitInputMethod(shell::Connector* connector) {
-  input_method_->Init(connector);
-}
-
 void WindowTreeHostMus::DispatchEvent(ui::Event* event) {
-  if (event->IsKeyEvent() && GetInputMethod()) {
-    GetInputMethod()->DispatchKeyEvent(event->AsKeyEvent());
-    return;
-  }
+  // Key events are sent to InputMethodMus directly from NativeWidgetMus.
+  DCHECK(!event->IsKeyEvent());
   WindowTreeHostPlatform::DispatchEvent(event);
 }