Fix git depot_tools update flow.

update_depot_tools

 #!/usr/bin/env bash
 # Copyright (c) 2011 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # This script will try to sync the bootstrap directories and then defer control.
 
 if [ "$USER" == "root" ];
 then
   echo Running depot tools as root is sad.
@@ skipping 67 matching lines @@
   OUTPUT=`"$GIT" svn rebase -q -q`
   if [[ ! "$OUTPUT" == *Current.branch* ]]; then
     echo $OUTPUT 1>&2
   fi
   cd - > /dev/null
 fi
 
 # We're on POSIX. We can now safely look for svn checkout.
 if [ "X$DEPOT_TOOLS_UPDATE" != "X0" -a -e "$base_dir/.svn" ]
 then
-  # Update the bootstrap directory to stay up-to-date with the latest
-  # depot_tools.
+  # Update the root directory to stay up-to-date with the latest depot_tools.
   BEFORE_REVISION=$(get_svn_revision)
   "$SVN" -q up "$base_dir"
   AFTER_REVISION=$(get_svn_revision)
   if [[ "$BEFORE_REVISION" != "$AFTER_REVISION" ]]; then
     echo "Depot Tools has been updated to revision $AFTER_REVISION." 1>&2
   fi
 fi
 
 find "$base_dir" -iname "*.pyc" -exec rm {} \;