[Offline Pages] Add a GCMAppHandler for offline page prefetch.

chrome/browser/offline_pages/prefetch/prefetch_service_factory.cc

 // Copyright 2017 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 "components/offline_pages/content/prefetch_service_factory.h"
+#include "chrome/browser/offline_pages/prefetch/prefetch_service_factory.h"
 
+#include "base/memory/ptr_util.h"
 #include "base/memory/singleton.h"
+#include "chrome/browser/gcm/gcm_profile_service_factory.h"
+#include "chrome/browser/offline_pages/prefetch/prefetch_gcm_app_handler.h"
+#include "components/gcm_driver/gcm_driver.h"
+#include "components/gcm_driver/gcm_profile_service.h"
 #include "components/keyed_service/content/browser_context_dependency_manager.h"
+#include "components/offline_pages/core/offline_page_feature.h"
 #include "components/offline_pages/core/prefetch/prefetch_service_impl.h"
 #include "content/public/browser/browser_context.h"
 
 namespace offline_pages {
 
 PrefetchServiceFactory::PrefetchServiceFactory()
     : BrowserContextKeyedServiceFactory(
           "OfflinePagePrefetchService",
-          BrowserContextDependencyManager::GetInstance()) {}
+          BrowserContextDependencyManager::GetInstance()) {
+  DependsOn(gcm::GCMProfileServiceFactory::GetInstance());
+}
 
 // static
 PrefetchServiceFactory* PrefetchServiceFactory::GetInstance() {
   return base::Singleton<PrefetchServiceFactory>::get();
 }
 
 // static
 PrefetchService* PrefetchServiceFactory::GetForBrowserContext(
     content::BrowserContext* context) {
   return static_cast<PrefetchService*>(
       GetInstance()->GetServiceForBrowserContext(context, true));
 }
 
 KeyedService* PrefetchServiceFactory::BuildServiceInstanceFor(
     content::BrowserContext* context) const {
-  return new PrefetchServiceImpl();
+  if (!offline_pages::IsPrefetchingOfflinePagesEnabled())

[Dmitry Titov, 2017/05/16 19:33:23]

It feels this check belongs to delayed initialization rather than to initial
lightweight creation of main objects. 

Also, I'm relying on PS being available unconditionally for my next CL of stats
accumulation (OfflineDaysAccumulator lives on PS).

I think all the objects injected here should be fine to be created regardless of
the flag. The actual work might not happening, but at least we don't need null
checks everywhere.

[dewittj, 2017/05/16 22:58:22]

Done.

+    return nullptr;
+
+  PrefetchGCMAppHandler* app_handler = new PrefetchGCMAppHandler();
+  auto service =
+      base::MakeUnique<PrefetchServiceImpl>(base::WrapUnique(app_handler));
+  gcm::GCMProfileServiceFactory::GetForProfile(context)
+      ->driver()
+      ->AddAppHandler(app_handler->app_id(), app_handler);
+  return service.release();
+}
+
+bool PrefetchServiceFactory::ServiceIsCreatedWithBrowserContext() const {

[Dmitry Titov, 2017/05/16 19:33:23]

Could you add a comment as to lightweight creation/delayed init?

[dewittj, 2017/05/16 22:58:22]

Done.

+  return true;
 }
 
 }  // namespace offline_pages