Decompose BrowserStateMonitor into two parts, simplifying unit tests and APIs.

chrome/browser/chromeos/input_method/browser_state_monitor.h

 // 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.
 
 #ifndef CHROME_BROWSER_CHROMEOS_INPUT_METHOD_BROWSER_STATE_MONITOR_H_
 #define CHROME_BROWSER_CHROMEOS_INPUT_METHOD_BROWSER_STATE_MONITOR_H_
 
 #include <string>
 
 #include "base/basictypes.h"
+#include "base/callback.h"
 #include "base/compiler_specific.h"
 #include "chrome/browser/chromeos/input_method/input_method_manager.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
-#include "content/public/browser/notification_types.h"
 
 namespace chromeos {
 namespace input_method {
 
-class InputMethodDelegate;
-
-// A class which monitors a notification from the browser to keep track of the
-// browser state (not logged in, logged in, etc.) and notify the current state
-// to the input method manager. The class also updates the appropriate Chrome
-// prefs via the InputMethodDelegate, depending on the current browser state.
-class BrowserStateMonitor : public content::NotificationObserver,
-                            public InputMethodManager::Observer {
+// Translates notifications from the browser (not logged in, logged in, etc.),
+// into InputMethodManager::State transitions.
+class BrowserStateMonitor : public content::NotificationObserver {
  public:
-  BrowserStateMonitor(InputMethodManager* manager,
-                      InputMethodDelegate* delegate);
+  // Constructs a monitor that will invoke the given observer callback whenever
+  // the InputMethodManager::State changes. Assumes that the current state is
+  // STATE_LOGIN_SCREEN.
+  explicit BrowserStateMonitor(
+      const base::Callback<void(InputMethodManager::State)>& observer);

[Seigo Nonaka, 2012/12/11 04:33:04]

nit: Can we pass null callback? please write comments.

[erikwright (departed), 2012/12/11 16:39:44]

Done.

   virtual ~BrowserStateMonitor();
 
   InputMethodManager::State state() const { return state_; }
 
- protected:
-  // InputMethodManager::Observer overrides:
-  virtual void InputMethodChanged(InputMethodManager* manager,
-                                  bool show_message) OVERRIDE;
-  virtual void InputMethodPropertyChanged(InputMethodManager* manager) OVERRIDE;
-
   // content::NotificationObserver overrides:
   virtual void Observe(int type,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
  private:
-  void SetState(InputMethodManager::State new_state);
-
-  InputMethodManager* manager_;
-  InputMethodDelegate* delegate_;
+  base::Callback<void(InputMethodManager::State)> observer_;
   InputMethodManager::State state_;
-
-  // This is used to register this object to some browser notifications.
   content::NotificationRegistrar notification_registrar_;
 
   DISALLOW_COPY_AND_ASSIGN(BrowserStateMonitor);
 };
 
 }  // namespace input_method
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_INPUT_METHOD_BROWSER_STATE_MONITOR_H_