Remove BrowserSignin, as it's not used anywhere.

chrome/browser/profiles/profile.cc

 // Copyright (c) 2011 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/profiles/profile.h"
 
 #include <string>
 
 #include "base/command_line.h"
 #include "base/compiler_specific.h"
@@ skipping 576 matching lines @@
 
   virtual ProfileSyncService* GetProfileSyncService() {
     return NULL;
   }
 
   virtual ProfileSyncService* GetProfileSyncService(
       const std::string& cros_user) {
     return NULL;
   }
 
-  virtual BrowserSignin* GetBrowserSignin() {
-    return profile_->GetBrowserSignin();
-  }
-
   virtual bool IsSameProfile(Profile* profile) {
     return (profile == this) || (profile == profile_);
   }
 
   virtual Time GetStartTime() const {
     return start_time_;
   }
 
   virtual SpellCheckHost* GetSpellCheckHost() {
     return profile_->GetSpellCheckHost();
@@ skipping 259 matching lines @@
 };
 #endif
 
 Profile* Profile::CreateOffTheRecordProfile() {
 #if defined(OS_CHROMEOS)
   if (Profile::IsGuestSession())
     return new GuestSessionProfile(this);
 #endif
   return new OffTheRecordProfileImpl(this);
 }