[SyncFS] Add an injection point to DriveService creation at SyncEngine::Initialize

chrome/browser/sync_file_system/drive_backend/sync_engine.h

Index: chrome/browser/sync_file_system/drive_backend/sync_engine.h
diff --git a/chrome/browser/sync_file_system/drive_backend/sync_engine.h b/chrome/browser/sync_file_system/drive_backend/sync_engine.h
index 8fb91a39ded43f57bbf0b4c8af7bb468a17aef77..e8e354a04e552967c5267f73bf2a0fa39da3e429 100644
--- a/chrome/browser/sync_file_system/drive_backend/sync_engine.h
+++ b/chrome/browser/sync_file_system/drive_backend/sync_engine.h
@@ -22,7 +22,7 @@
 #include "net/base/network_change_notifier.h"
 
 class ExtensionServiceInterface;
-class ProfileOAuth2TokenService;
+class OAuth2TokenService;
 
 namespace base {
 class SequencedTaskRunner;
@@ -65,6 +65,19 @@ class SyncEngine : public RemoteFileSyncService,
  public:
   typedef RemoteFileSyncService::Observer SyncServiceObserver;
 
+  class DriveServiceFactory {
+   public:
+    DriveServiceFactory() {}
+    virtual ~DriveServiceFactory() {}
+    virtual scoped_ptr<drive::DriveServiceInterface> CreateDriveService(
+        OAuth2TokenService* oauth2_token_service,
+        net::URLRequestContextGetter* url_request_context_getter,
+        base::SequencedTaskRunner* blocking_task_runner);
+
+   private:
+    DISALLOW_COPY_AND_ASSIGN(DriveServiceFactory);
+  };
+
   static scoped_ptr<SyncEngine> CreateForBrowserContext(
       content::BrowserContext* context,
       TaskLogger* task_logger);
@@ -154,8 +167,9 @@ class SyncEngine : public RemoteFileSyncService,
              drive::DriveNotificationManager* notification_manager,
              ExtensionServiceInterface* extension_service,
              SigninManagerBase* signin_manager,
-             ProfileOAuth2TokenService* token_service,
+             OAuth2TokenService* token_service,
              net::URLRequestContextGetter* request_context,
+             scoped_ptr<DriveServiceFactory> drive_service_factory,
              leveldb::Env* env_override);
 
   // Called by WorkerObserver.
@@ -183,10 +197,12 @@ class SyncEngine : public RemoteFileSyncService,
   drive::DriveNotificationManager* notification_manager_;
   ExtensionServiceInterface* extension_service_;
   SigninManagerBase* signin_manager_;
-  ProfileOAuth2TokenService* token_service_;
+  OAuth2TokenService* token_service_;
 
   scoped_refptr<net::URLRequestContextGetter> request_context_;
 
+  scoped_ptr<DriveServiceFactory> drive_service_factory_;
+
   scoped_ptr<drive::DriveServiceInterface> drive_service_;
   scoped_ptr<DriveServiceWrapper> drive_service_wrapper_;
   scoped_ptr<drive::DriveUploaderInterface> drive_uploader_;