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

chrome/browser/chrome_to_mobile_service_factory.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_CHROME_TO_MOBILE_SERVICE_FACTORY_H_
 #define CHROME_BROWSER_CHROME_TO_MOBILE_SERVICE_FACTORY_H_
 
 #include "base/compiler_specific.h"
 #include "base/memory/singleton.h"
 #include "chrome/browser/profiles/profile_keyed_service_factory.h"
 
 class ChromeToMobileService;
 
 class ChromeToMobileServiceFactory : public ProfileKeyedServiceFactory {
  public:
   // Get the singleton ChromeToMobileServiceFactory instance.
   static ChromeToMobileServiceFactory* GetInstance();
 
   // Get |profile|'s ChromeToMobileService, creating one if needed.
   static ChromeToMobileService* GetForProfile(Profile* profile);
 
  protected:
   // ProfileKeyedServiceFactory overrides:
   virtual ProfileKeyedService* BuildServiceInstanceFor(
       Profile* profile) const OVERRIDE;
 
  private:
   friend struct DefaultSingletonTraits<ChromeToMobileServiceFactory>;
 
-  explicit ChromeToMobileServiceFactory();
+  ChromeToMobileServiceFactory();
   virtual ~ChromeToMobileServiceFactory();
 
   DISALLOW_COPY_AND_ASSIGN(ChromeToMobileServiceFactory);
 };
 
 #endif  // CHROME_BROWSER_CHROME_TO_MOBILE_SERVICE_FACTORY_H_