Implement TouchFile on drive::FileSystem.

chrome/browser/chromeos/drive/file_system/drive_operations.h

Index: chrome/browser/chromeos/drive/file_system/drive_operations.h
diff --git a/chrome/browser/chromeos/drive/file_system/drive_operations.h b/chrome/browser/chromeos/drive/file_system/drive_operations.h
index d8c5dca7a18eb685d8f7c753c8fc7d1d50f8d5bb..dd6fe1e1da7921b270b757e925ace660a8f7573b 100644
--- a/chrome/browser/chromeos/drive/file_system/drive_operations.h
+++ b/chrome/browser/chromeos/drive/file_system/drive_operations.h
@@ -11,6 +11,7 @@
 namespace base {
 class FilePath;
 class SequencedTaskRunner;
+class Time;
 }  // namespace base
 
 namespace drive {
@@ -31,6 +32,7 @@ class MoveOperation;
 class OperationObserver;
 class RemoveOperation;
 class SearchOperation;
+class TouchOperation;
 class UpdateOperation;
 
 // Callback for DriveOperations::Search.
@@ -106,6 +108,13 @@ class DriveOperations {
               bool is_recursive,
               const FileOperationCallback& callback);
 
+  // Wrapper function for touch_operation_.
+  // |callback| must not be null.
+  void TouchFile(const base::FilePath& file_path,
+                 const base::Time& last_access_time,
+                 const base::Time& last_modified_time,
+                 const FileOperationCallback& callback);
+
   // Wrapper function for update_operation_.
   // |callback| must not be null.
   void UpdateFileByResourceId(const std::string& resource_id,
@@ -124,6 +133,7 @@ class DriveOperations {
   scoped_ptr<CreateFileOperation> create_file_operation_;
   scoped_ptr<MoveOperation> move_operation_;
   scoped_ptr<RemoveOperation> remove_operation_;
+  scoped_ptr<TouchOperation> touch_operation_;
   scoped_ptr<UpdateOperation> update_operation_;
   scoped_ptr<SearchOperation> search_operation_;
 };