Simplify InputMethodWin initialization.

ui/base/ime/input_method_mac.mm

 // Copyright 2014 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_mac.h"
 
 namespace ui {
 
 InputMethodMac::InputMethodMac(internal::InputMethodDelegate* delegate) {
   SetDelegate(delegate);
@@ skipping 18 matching lines @@
 void InputMethodMac::CancelComposition(const TextInputClient* client) {
 }
 
 void InputMethodMac::OnInputLocaleChanged() {
 }
 
 std::string InputMethodMac::GetInputLocale() {
   return "";
 }
 
-bool InputMethodMac::IsActive() {
-  return true;
-}
-
 bool InputMethodMac::IsCandidatePopupOpen() const {
   // There seems to be no way to tell if a candidate window is open.
   return false;
 }
 
 }  // namespace ui