Remove BrowserSignin, as it's not used anywhere.

chrome/browser/extensions/extension_function_dispatcher.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/extensions/extension_function_dispatcher.h"
 
 #include <map>
 
 #include "base/memory/ref_counted.h"
 #include "base/memory/singleton.h"
@@ skipping 316 matching lines @@
 
   // Extension module.
   RegisterFunction<SetUpdateUrlDataFunction>();
   RegisterFunction<IsAllowedIncognitoAccessFunction>();
   RegisterFunction<IsAllowedFileSchemeAccessFunction>();
 
   // WebstorePrivate.
   RegisterFunction<GetBrowserLoginFunction>();
   RegisterFunction<GetStoreLoginFunction>();
   RegisterFunction<SetStoreLoginFunction>();
-  RegisterFunction<PromptBrowserLoginFunction>();
   RegisterFunction<BeginInstallFunction>();
   RegisterFunction<BeginInstallWithManifestFunction>();
   RegisterFunction<CompleteInstallFunction>();
 
   // WebNavigation.
   RegisterFunction<GetFrameFunction>();
 
   // WebRequest.
   RegisterFunction<WebRequestAddEventListener>();
   RegisterFunction<WebRequestEventHandled>();
@@ skipping 299 matching lines @@
   return function;
 }
 
 // static
 void ExtensionFunctionDispatcher::SendAccessDenied(
     IPC::Message::Sender* ipc_sender, int routing_id, int request_id) {
   ipc_sender->Send(new ExtensionMsg_Response(
       routing_id, request_id, false, std::string(),
       "Access to extension API denied."));
 }