depot_tools: Add .html and .css to git-gs.

git-gs

Index: git-gs
===================================================================
--- git-gs	(revision 55660)
+++ git-gs	(working copy)
@@ -1,9 +1,9 @@
 #!/bin/sh
-# Copyright (c) 2009 The Chromium Authors. All rights reserved.
+# Copyright (c) 2010 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.
 git grep -n -e "$@" -- "*.h" "*.hpp" "*.cpp" "*.c" "*.cc" "*.cpp" "*.inl"\
    "*.grd" "*.idl" "*.m" "*.mm" "*.py" "*.sh" "*.cfg"\
    "*SConscript" "SConscript*" "*.scons" "*.vcproj" "*.vsprops" "*.make"\
-   "*.gyp" "*.gypi" "*.js"
+   "*.gyp" "*.gypi" "*.js" "*.html" "*.css"