Change some functions in ImeEngineObserver as not ChromeOS-only.

chrome/browser/extensions/api/input_ime/input_ime_api_nonchromeos.cc

 // Copyright 2015 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.
 
 // This file is for non-chromeos (win & linux) functions, such as
 // chrome.input.ime.activate, chrome.input.ime.createWindow and
 // chrome.input.ime.onSelectionChanged.
 // TODO(azurewei): May refactor the code structure by using delegate or
 // redesign the API to remove this platform-specific file in the future.
 
@@ skipping 29 matching lines @@
       return;
     }
 
     scoped_ptr<extensions::Event> event(
         new extensions::Event(histogram_value, event_name, std::move(args)));
     event->restrict_to_browser_context = profile_;
     extensions::EventRouter::Get(profile_)
         ->DispatchEventToExtension(extension_id_, std::move(event));
   }
 
+  std::string GetCurrentScreenType() override {
+    return "normal";
+  }
+
   DISALLOW_COPY_AND_ASSIGN(ImeObserverNonChromeOS);
 };
 
 }  // namespace
 
 namespace extensions {
 
 bool InputImeEventRouter::RegisterImeExtension(
     const std::string& extension_id,
     const std::vector<extensions::InputComponentInfo>& input_components) {
   return false;
 }
 
 void InputImeEventRouter::UnregisterAllImes(const std::string& extension_id) {}
 
 }  // namespace extensions