Implement polling part of DriveFileSyncService

chrome/browser/sync_file_system/drive_file_sync_service.h

Index: chrome/browser/sync_file_system/drive_file_sync_service.h
diff --git a/chrome/browser/sync_file_system/drive_file_sync_service.h b/chrome/browser/sync_file_system/drive_file_sync_service.h
index 04ddeffcb4f1dcac5ab94f7a447c0ba291094eb3..292c761e2e4bd14c8c0bf71df9adea34137a5fd3 100644
--- a/chrome/browser/sync_file_system/drive_file_sync_service.h
+++ b/chrome/browser/sync_file_system/drive_file_sync_service.h
@@ -16,6 +16,7 @@
 #include "base/memory/weak_ptr.h"
 #include "base/observer_list.h"
 #include "base/threading/non_thread_safe.h"
+#include "base/timer.h"
 #include "chrome/browser/google_apis/drive_service_interface.h"
 #include "chrome/browser/google_apis/gdata_wapi_parser.h"
 #include "chrome/browser/sync_file_system/local_change_processor.h"
@@ -277,7 +278,7 @@ class DriveFileSyncService
       fileapi::SyncStatusCode status);
 
   void AppendNewRemoteChange(const GURL& origin,
-                             google_apis::DocumentEntry* entry,
+                             const google_apis::DocumentEntry& entry,
                              int64 changestamp,
                              RemoteSyncType sync_type);
   void CancelRemoteChange(const fileapi::FileSystemURL& url);
@@ -289,6 +290,14 @@ class DriveFileSyncService
 
   FilePath temporary_file_dir_;
 
+  void FetchChangesForIncrementalSync();
+  void DidFetchChangesForIncrementalSync(
+      scoped_ptr<TaskToken> token,
+      google_apis::GDataErrorCode error,
+      scoped_ptr<google_apis::DocumentFeed> changes);
+  bool GetOriginForEntry(const google_apis::DocumentEntry& entry, GURL* origin);
+  void SchedulePolling();
+
   scoped_ptr<DriveMetadataStore> metadata_store_;
   scoped_ptr<DriveFileSyncClient> sync_client_;
 
@@ -296,7 +305,9 @@ class DriveFileSyncService
   RemoteServiceState state_;
   std::deque<base::Closure> pending_tasks_;
 
-  int64 largest_changestamp_;
+  int64 largest_synced_changestamp_;
+  int64 largest_fetched_changestamp_;
+
   PendingChangeQueue pending_changes_;
   URLToChange url_to_change_;
 
@@ -309,6 +320,9 @@ class DriveFileSyncService
   // NotifyTaskDone when the task finished.
   scoped_ptr<TaskToken> token_;
 
+  base::OneShotTimer<DriveFileSyncService> polling_timer_;
+  base::TimeDelta polling_delay_;
+
   ObserverList<Observer> observers_;
 
   // Use WeakPtrFactory instead of SupportsWeakPtr to revoke the weak pointer