Make DispatchKeyEventPostIME() asynchronous.

ui/base/ime/input_method_delegate.cc

Index: ui/base/ime/input_method_delegate.cc
diff --git a/ui/base/ime/input_method_delegate.cc b/ui/base/ime/input_method_delegate.cc
new file mode 100644
index 0000000000000000000000000000000000000000..42802c0015b70c45229e6dc275beb65920e41aaf
--- /dev/null
+++ b/ui/base/ime/input_method_delegate.cc
@@ -0,0 +1,23 @@
+// 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 "ui/base/ime/input_method_delegate.h"
+
+#include "base/callback.h"
+#include "ui/events/event.h"
+
+namespace ui {
+namespace internal {
+
+ui::EventDispatchDetails InputMethodDelegate::DispatchKeyEventPostIME(
+    ui::KeyEvent* key_event,
+    std::unique_ptr<base::Callback<void(bool)>> ack_callback) {
+  ui::EventDispatchDetails details = DispatchKeyEventPostIME(key_event);
+  if (ack_callback)
+    ack_callback->Run(key_event->stopped_propagation());
+  return details;
+}
+
+}  // namespace internal
+}  // namespace ui