Lazy initialization for ExtensionInputMethodEventRouter

chrome/browser/chromeos/extensions/input_method_api.cc

 // Copyright (c) 2012 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 "chrome/browser/chromeos/extensions/input_method_api.h"
 
 #include "base/values.h"
 #include "chrome/browser/chromeos/extensions/input_method_event_router.h"
 #include "chrome/browser/chromeos/input_method/input_method_configuration.h"
 #include "chrome/browser/chromeos/input_method/input_method_manager.h"
-#include "chrome/browser/extensions/extension_service.h"
+#include "chrome/browser/extensions/event_names.h"
 #include "chrome/browser/extensions/extension_system.h"
 #include "chrome/browser/profiles/profile.h"
 
+namespace {
+
+// Prefix, which is used by XKB.
+const char kXkbPrefix[] = "xkb:";
+
+}  // namespace
+
 namespace extensions {
 
 GetInputMethodFunction::GetInputMethodFunction() {
 }
 
 GetInputMethodFunction::~GetInputMethodFunction() {
 }
 
 bool GetInputMethodFunction::RunImpl() {
 #if !defined(OS_CHROMEOS)
   NOTREACHED();
   return false;
 #else
-  chromeos::ExtensionInputMethodEventRouter* router =
-      extensions::ExtensionSystem::Get(profile_)->extension_service()->
-          input_method_event_router();
   chromeos::input_method::InputMethodManager* manager =
       chromeos::input_method::GetInputMethodManager();
-  const std::string input_method =
-      router->GetInputMethodForXkb(manager->GetCurrentInputMethod().id());
+  const std::string input_method = InputMethodAPI::GetInputMethodForXkb(
+      manager->GetCurrentInputMethod().id());
   SetResult(Value::CreateStringValue(input_method));
   return true;
 #endif
 }
 
+InputMethodAPI::InputMethodAPI(Profile* profile)
+    : profile_(profile) {
+  ExtensionSystem::Get(profile_)->event_router()->RegisterObserver(
+      this, event_names::kOnInputMethodChanged);
+}
+
+InputMethodAPI::~InputMethodAPI() {
+}
+
+// static
+std::string InputMethodAPI::GetInputMethodForXkb(const std::string& xkb_id) {
+  size_t prefix_length = std::string(kXkbPrefix).length();
+  DCHECK(xkb_id.substr(0, prefix_length) == kXkbPrefix);
+  return xkb_id.substr(prefix_length);
+}
+
+void InputMethodAPI::Shutdown() {
+  // UnregisterObserver may have already been called in OnListenerAdded,
+  // but it is safe to call it more than once.
+  ExtensionSystem::Get(profile_)->event_router()->UnregisterObserver(this);
+}
+
+void InputMethodAPI::OnListenerAdded(
+    const extensions::EventListenerInfo& details) {
+  DCHECK(!input_method_event_router_.get());
+  input_method_event_router_.reset(
+      new chromeos::ExtensionInputMethodEventRouter());
+  ExtensionSystem::Get(profile_)->event_router()->UnregisterObserver(this);
+}
+
 }  // namespace extensions