chromeos: Add DriveFileSystem::Pin/Unpin

chrome/browser/chromeos/drive/drive_file_system_interface.h

Index: chrome/browser/chromeos/drive/drive_file_system_interface.h
diff --git a/chrome/browser/chromeos/drive/drive_file_system_interface.h b/chrome/browser/chromeos/drive/drive_file_system_interface.h
index 7ae18dd7a6fb6754861d3a60d744283f709b2379..354b7dadcd9add01cffd461e67db1c8fea59cf5b 100644
--- a/chrome/browser/chromeos/drive/drive_file_system_interface.h
+++ b/chrome/browser/chromeos/drive/drive_file_system_interface.h
@@ -282,6 +282,18 @@ class DriveFileSystemInterface {
                           bool is_exclusive,
                           const FileOperationCallback& callback) = 0;
 
+  // Pins a file at |file_path|.
+  //
+  // |callback| must not be null.
+  virtual void Pin(const base::FilePath& file_path,
+                   const FileOperationCallback& callback) = 0;
+
+  // Unpins a file at |file_path|.
+  //
+  // |callback| must not be null.
+  virtual void Unpin(const base::FilePath& file_path,
+                     const FileOperationCallback& callback) = 0;
+
   // Gets |file_path| from the file system. The file entry represented by
   // |file_path| needs to be present in in-memory representation of the file
   // system in order to be retrieved. If the file is not cached, the file