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

bootstrap/win/7z.readme.txt

Index: bootstrap/win/7z.readme.txt
===================================================================
--- bootstrap/win/7z.readme.txt	(revision 14956)
+++ bootstrap/win/7z.readme.txt	(working copy)
@@ -1,42 +0,0 @@
-7-Zip Command line version 4.65
--------------------------------
-
-7-Zip is a file archiver with high compression ratio.
-7za.exe is a standalone command line version of 7-Zip.
-
-7-Zip Copyright (C) 1999-2009 Igor Pavlov.
-
-Features of 7za.exe: 
-  - High compression ratio in new 7z format
-  - Supported formats:
-      - Packing / unpacking: 7z, ZIP, GZIP, BZIP2 and TAR 
-      - Unpacking only: Z
-  - Highest compression ratio for ZIP and GZIP formats.
-  - Fast compression and decompression
-  - Strong AES-256 encryption in 7z and ZIP formats.
-
-7za.exe is a free software distributed under the GNU LGPL.
-Read license.txt for more information.
-
-Source code of 7za.exe and 7-Zip can be found at
-http://www.7-zip.org/
-
-7za.exe can work in Windows 95/98/ME/NT/2000/XP/2003/Vista.
-
-There is also port of 7za.exe for POSIX systems like Unix (Linux, Solaris, OpenBSD, 
-FreeBSD, Cygwin, AIX, ...), MacOS X and BeOS:
-
-http://p7zip.sourceforge.net/
-
-
-  This distributive packet contains the following files:
-
-  7za.exe       - 7-Zip standalone command line version.
-  readme.txt    - This file.
-  copying.txt   - GNU LGPL license.
-  license.txt   - License information.
-  7-zip.chm     - User's Manual in HTML Help format.
-
-
----
-End of document