Extract InstallVerifier from ExtensionSystem.

extensions/shell/browser/shell_extension_system.cc

 // Copyright 2014 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 "extensions/shell/browser/shell_extension_system.h"
 
 #include <string>
 
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
@@ skipping 130 matching lines @@
 }
 
 LazyBackgroundTaskQueue* ShellExtensionSystem::lazy_background_task_queue() {
   return lazy_background_task_queue_.get();
 }
 
 EventRouter* ShellExtensionSystem::event_router() {
   return event_router_.get();
 }
 
-InstallVerifier* ShellExtensionSystem::install_verifier() {
-  return nullptr;
-}
-
 QuotaService* ShellExtensionSystem::quota_service() {
   return quota_service_.get();
 }
 
 void ShellExtensionSystem::RegisterExtensionWithRequestContexts(
     const Extension* extension) {
   BrowserThread::PostTask(BrowserThread::IO,
                           FROM_HERE,
                           base::Bind(&InfoMap::AddExtension,
                                      info_map(),
@@ skipping 15 matching lines @@
 ContentVerifier* ShellExtensionSystem::content_verifier() {
   return nullptr;
 }
 
 scoped_ptr<ExtensionSet> ShellExtensionSystem::GetDependentExtensions(
     const Extension* extension) {
   return make_scoped_ptr(new ExtensionSet());
 }
 
 }  // namespace extensions