[ew] Add basic classes.

chrome/browser/sync_file_system/local/sync_file_system_backend.cc

Index: chrome/browser/sync_file_system/local/sync_file_system_backend.cc
diff --git a/chrome/browser/sync_file_system/local/sync_file_system_backend.cc b/chrome/browser/sync_file_system/local/sync_file_system_backend.cc
index c6b620cd06b7ee950a81600d0eb690c834de1fc3..8f9045754e348ad8a75ec0f43f24d501a04af2fc 100644
--- a/chrome/browser/sync_file_system/local/sync_file_system_backend.cc
+++ b/chrome/browser/sync_file_system/local/sync_file_system_backend.cc
@@ -4,6 +4,8 @@
 
 #include "chrome/browser/sync_file_system/local/sync_file_system_backend.h"
 
+#include <string>
+
 #include "base/logging.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/sync_file_system/local/local_file_change_tracker.h"
@@ -138,6 +140,11 @@ storage::AsyncFileUtil* SyncFileSystemBackend::GetAsyncFileUtil(
   return GetDelegate()->file_util();
 }
 
+storage::WatcherManager* SyncFileSystemBackend::GetWatcherManager(
+    storage::FileSystemType type) {
+  return NULL;
+}
+
 storage::CopyOrMoveFileValidatorFactory*
 SyncFileSystemBackend::GetCopyOrMoveFileValidatorFactory(
     storage::FileSystemType type,