Bump git bleeding edge up to 6.

bootstrap/win/win_tools.bat

 @echo off
 :: Copyright (c) 2012 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 find if svn and python are accessible and it not,
 :: it will try to download it and 'install' it in depot_tools.
 
 :: Sadly, we can't use SETLOCAL here otherwise it ERRORLEVEL is not correctly
 :: returned.
@@ skipping 50 matching lines @@
 
 :GIT_CHECK
 goto :GIT_190_CHECK
 
 
 :GIT_190_CHECK
 set GIT_ERASE_TOP=4
 set GIT_VERSION=1.9.0.chromium.5
 
 if not "%DEPOT_TOOLS_GIT_BLEEDING%" == "1" goto :GIT_190_CHECK_REST
-set GIT_ERASE_TOP=4
-set GIT_VERSION=1.9.0.chromium.5
+set GIT_ERASE_TOP=5
+set GIT_VERSION=1.9.0.chromium.6
 
 :GIT_190_CHECK_REST
 if "%DEPOT_TOOLS_GIT_190%" == "0" goto :GIT_1852_CHECK
 :: Clean up a couple of known broken releases
 for /l %%i in (1,1,%GIT_ERASE_TOP%) do if exist "%WIN_TOOLS_ROOT_DIR%\git-1.9.0.chromium.%%i_bin" (
   rmdir /s /q "%WIN_TOOLS_ROOT_DIR%\git-1.9.0.chromium.%%i_bin"
 )
 for /f "tokens=2 delims=[]" %%i in ('ver') do set VERSTR=%%i
 for /f "tokens=2,3 delims=. " %%i in ("%VERSTR%") do (set VERMAJOR=%%i & set VERMINOR=%%j)
 if %VERMAJOR% lss 5 set GIT_VERSION=%GIT_VERSION%-xp
@@ skipping 124 matching lines @@
 goto :END
 
 
 :returncode
 set WIN_TOOLS_ROOT_URL=
 set WIN_TOOLS_ROOT_DIR=
 exit /b %ERRORLEVEL%
 
 :END
 call :returncode %ERRORLEVEL%