Add missing (and remove superfluous) 'explicit' from constructors.

chrome/browser/ui/cocoa/browser/avatar_button_controller.mm

 // 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.
 
 #import "chrome/browser/ui/cocoa/browser/avatar_button_controller.h"
 
 #include "base/sys_string_conversions.h"
 #include "chrome/app/chrome_command_ids.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/command_updater.h"
@@ skipping 31 matching lines @@
 // Declare a 10.7+ private API.
 // NSThemeFrame < NSTitledFrame < NSFrameView < NSView.
 @interface NSView (NSThemeFrame)
 - (void)_tileTitlebarAndRedisplay:(BOOL)redisplay;
 @end
 
 namespace AvatarButtonControllerInternal {
 
 class Observer : public content::NotificationObserver {
  public:
-  Observer(AvatarButtonController* button) : button_(button) {
+  explicit Observer(AvatarButtonController* button) : button_(button) {
     registrar_.Add(this, chrome::NOTIFICATION_PROFILE_CACHED_INFO_CHANGED,
                    content::NotificationService::AllSources());
   }
 
   // NotificationObserver:
   virtual void Observe(int type,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE {
     switch (type) {
       case chrome::NOTIFICATION_PROFILE_CACHED_INFO_CHANGED:
@@ skipping 240 matching lines @@
     [themeFrame _tileTitlebarAndRedisplay:YES];
 }
 
 // Testing /////////////////////////////////////////////////////////////////////
 
 - (AvatarMenuBubbleController*)menuController {
   return menuController_;
 }
 
 @end