Split ExtensionSystem interface from ExtensionSystemImpl implementation, part 1.

chrome/browser/extensions/extension_installer.cc

 // Copyright (c) 2013 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_installer.h"
 
 #include "base/bind.h"
-#include "chrome/browser/extensions/extension_system.h"
 #include "chrome/browser/profiles/profile.h"
 #include "content/public/browser/browser_thread.h"
+#include "extensions/browser/extension_system.h"
 #include "extensions/browser/management_policy.h"
 
 namespace extensions {
 
 ExtensionInstaller::ExtensionInstaller(Profile* profile)
     : requirements_checker_(new RequirementsChecker()),
       profile_(profile),
       weak_ptr_factory_(this) {
 }
 
 ExtensionInstaller::~ExtensionInstaller() {
 }
 
 void ExtensionInstaller::CheckRequirements(
     const RequirementsCallback& callback) {
   DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
   requirements_checker_->Check(extension_, callback);
 }
 
 base::string16 ExtensionInstaller::CheckManagementPolicy() {
   base::string16 error;
   bool allowed = ExtensionSystem::Get(profile_)->management_policy()
       ->UserMayLoad(extension_.get(), &error);
   DCHECK(allowed || !error.empty());
   return error;
 }
 
 }  // namespace extensions