Adding ClearBlackList to the PreviewsBlackList and plumbing to UI

chrome/browser/previews/previews_service_factory.cc

 // Copyright 2016 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/previews/previews_service_factory.h"
 
 #include "chrome/browser/previews/previews_service.h"
 #include "chrome/browser/profiles/profile.h"
 #include "components/keyed_service/content/browser_context_dependency_manager.h"
 #include "content/public/browser/browser_context.h"
 
 namespace {
 
 base::LazyInstance<PreviewsServiceFactory> g_previews_factory =
     LAZY_INSTANCE_INITIALIZER;
 
 }  // namespace
 
 // static
 PreviewsService* PreviewsServiceFactory::GetForProfile(Profile* profile) {
-  DCHECK_NE(profile->GetProfileType(), Profile::INCOGNITO_PROFILE);
   return static_cast<PreviewsService*>(
       GetInstance()->GetServiceForBrowserContext(profile, true));
 }
 
 // static
 PreviewsServiceFactory* PreviewsServiceFactory::GetInstance() {
   return g_previews_factory.Pointer();
 }
 
 PreviewsServiceFactory::PreviewsServiceFactory()
     : BrowserContextKeyedServiceFactory(
           "PreviewsService",
           BrowserContextDependencyManager::GetInstance()) {}
 
 PreviewsServiceFactory::~PreviewsServiceFactory() {}
 
 KeyedService* PreviewsServiceFactory::BuildServiceInstanceFor(
     content::BrowserContext* context) const {
   return new PreviewsService();
 }