Only add unstaged baseline changes to the git index when rebaselining.

third_party/WebKit/Tools/Scripts/webkitpy/common/checkout/scm/scm.py

 # Copyright (c) 2009, Google Inc. All rights reserved.
 # Copyright (c) 2009 Apple Inc. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 # notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
@@ skipping 103 matching lines @@
 
     def delete_list(self, paths):
         self._subclass_must_implement()
 
     def move(self, origin, destination):
         self._subclass_must_implement()
 
     def exists(self, path):
         self._subclass_must_implement()
 
+    def unstaged_changes(self):
+        self._subclass_must_implement()
+
     def changed_files(self, git_commit=None):
         self._subclass_must_implement()
 
     def _added_files(self):
         self._subclass_must_implement()
 
     def _deleted_files(self):
         self._subclass_must_implement()
 
     def display_name(self):
@@ skipping 15 matching lines @@
     #--------------------------------------------------------------------------
     # Subclasses must indicate if they support local commits,
     # but the SCM baseclass will only call local_commits methods when this is true.
     @staticmethod
     def supports_local_commits():
         SCM._subclass_must_implement()
 
     def commit_locally_with_message(self, message):
         _log.error("Your source control manager does not support local commits.")
         sys.exit(1)