Add unzip.js instead of using 7za.exe. It greatly reduces the depot_tools.zip...

bootstrap/win/7z.license.txt

-      7-Zip Command line version
-      ~~~~~~~~~~~~~~~~~~~~~~~~~~
-      License for use and distribution
-      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-      7-Zip Copyright (C) 1999-2009 Igor Pavlov.
-
-      7za.exe is distributed under the GNU LGPL license
-
-      Notes: 
-        You can use 7-Zip on any computer, including a computer in a commercial 
-        organization. You don't need to register or pay for 7-Zip.
-
-
-      GNU LGPL information
-      --------------------
-
-        This library is free software; you can redistribute it and/or
-        modify it under the terms of the GNU Lesser General Public
-        License as published by the Free Software Foundation; either
-        version 2.1 of the License, or (at your option) any later version.
-
-        This library is distributed in the hope that it will be useful,
-        but WITHOUT ANY WARRANTY; without even the implied warranty of
-        MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-        Lesser General Public License for more details.
-
-        You should have received a copy of the GNU Lesser General Public
-        License along with this library; if not, write to the Free Software
-        Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA