Make DrMemory update process reliable

tools/valgrind/chrome_tests.bat

 @echo off
 :: 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.
 
-:: TODO(timurrrr): batch files 'export' all the variables to the parent shell
+setlocal
+
 set THISDIR=%~dp0
 set TOOL_NAME="unknown"
 
 :: Get the tool name and put it into TOOL_NAME {{{1
 :: NB: SHIFT command doesn't modify %*
 :PARSE_ARGS_LOOP
   if %1 == () GOTO:TOOLNAME_NOT_FOUND
   if %1 == --tool GOTO:TOOLNAME_FOUND
   SHIFT
   goto :PARSE_ARGS_LOOP
 
 :TOOLNAME_NOT_FOUND
 echo "Please specify a tool (tsan or drmemory) by using --tool flag"
 exit /B 1
 
 :TOOLNAME_FOUND
 SHIFT
 set TOOL_NAME=%1
 :: }}}
 if "%TOOL_NAME%" == "drmemory"          GOTO :SETUP_DRMEMORY
 if "%TOOL_NAME%" == "drmemory_light"    GOTO :SETUP_DRMEMORY
 if "%TOOL_NAME%" == "drmemory_full"     GOTO :SETUP_DRMEMORY
 if "%TOOL_NAME%" == "drmemory_pattern"  GOTO :SETUP_DRMEMORY
 if "%TOOL_NAME%" == "tsan"     GOTO :SETUP_TSAN
 echo "Unknown tool: `%TOOL_NAME%`! Only tsan and drmemory are supported right now"
 exit /B 1
 
 :SETUP_DRMEMORY
-if NOT "%DRMEMORY_COMMAND%"=="" GOTO :RUN_TESTS

[the_wrong_timurrrr_2, 2016/03/18 15:23:50]

No, you shouldn't remove this line.
This line is very useful if one wants to test a custom build of Dr.Memory, e.g.
during DrM development.

 :: Set up DRMEMORY_COMMAND to invoke Dr. Memory {{{1
 set DRMEMORY_PATH=%THISDIR%..\..\third_party\drmemory
 set DRMEMORY_SFX=%DRMEMORY_PATH%\drmemory-windows-sfx.exe
 if EXIST %DRMEMORY_SFX% GOTO DRMEMORY_BINARY_OK
 echo "Can't find Dr. Memory executables."
 echo "See http://www.chromium.org/developers/how-tos/using-valgrind/dr-memory"
 echo "for the instructions on how to get them."
 exit /B 1
 
 :DRMEMORY_BINARY_OK
@@ skipping 15 matching lines @@
 :TSAN_BINARY_OK
 %TSAN_SFX% -o%TSAN_PATH%\unpacked -y
 set PIN_COMMAND=%TSAN_PATH%\unpacked\tsan-x86-windows\tsan.bat
 :: }}}
 goto :RUN_TESTS
 
 :RUN_TESTS
 set PYTHONPATH=%THISDIR%../python/google
 set RUNNING_ON_VALGRIND=yes
 python %THISDIR%/chrome_tests.py %*