Enable Config::MUS to use classic IME instead of servicified IME.

ash/mus/ash_window_tree_host_mus.cc

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ash/mus/ash_window_tree_host_mus.h"
 
 #include "ash/host/root_window_transformer.h"
 #include "ash/host/transformer_helper.h"
+#include "ash/ime/input_method_event_handler.h"
 #include "base/memory/ptr_util.h"
 #include "ui/aura/mus/window_tree_host_mus_init_params.h"
 #include "ui/aura/window.h"
+#include "ui/events/event_sink.h"
 #include "ui/events/null_event_targeter.h"
 
 namespace ash {
 
 AshWindowTreeHostMus::AshWindowTreeHostMus(
     aura::WindowTreeHostMusInitParams init_params)
     : aura::WindowTreeHostMus(std::move(init_params)),
       transformer_helper_(base::MakeUnique<TransformerHelper>(this)) {
   transformer_helper_->Init();
 }
@@ skipping 55 matching lines @@
 
 gfx::Transform AshWindowTreeHostMus::GetInverseRootTransform() const {
   return transformer_helper_->GetInverseTransform();
 }
 
 void AshWindowTreeHostMus::UpdateRootWindowSizeInPixels(
     const gfx::Size& host_size_in_pixels) {
   transformer_helper_->UpdateWindowSize(host_size_in_pixels);
 }
 
+ui::EventDispatchDetails AshWindowTreeHostMus::DispatchKeyEventPostIME(

[sky, 2017/05/04 03:09:18]

Can you elaborate on why this is the right fix? Why doesn't
SendEventToSink(event) work in this case?

[Hadi, 2017/05/04 12:15:17]

The implementation here was based on what AshWindowTreeHostPlatform does in this
case.

We could use SendEventToSink() instead of event_sink()->OnEventFromSource(). I
made this change.

The reason for SetPostIME(true)/(false): When execution reaches here, we are
still executing InputMethodEventHandler::OnKeyEvent(). If we don't disable it
for SendEventToSink() here, we get an infinite recursion since
InputMethodEventHandler will be tried again. When code reaches here it means
that the input method logic couldn't handle the event and wants to see if there
is anything other than IME that can handle the key event.

(Actually I am thinking what are the consequences of removing
DispatchKeyEventPostIME(), and letting ui::EventDispatcher try the post IME
handlers and targets; But for the sake of this CL, this implementation of
DispatchKeyEventPostIME is to avoid infinite recursion).

+    ui::KeyEvent* event) {
+  input_method_handler()->SetPostIME(true);
+  ui::EventDispatchDetails details = event_sink()->OnEventFromSource(event);
+  if (!details.dispatcher_destroyed)
+    input_method_handler()->SetPostIME(false);
+  return details;
+}
+
 }  // namespace ash