[chromedriver] Remove _CleanTmpDir and use $TMPDIR directly on bots.

chrome/test/chromedriver/run_buildbot_steps.py

Index: chrome/test/chromedriver/run_buildbot_steps.py
diff --git a/chrome/test/chromedriver/run_buildbot_steps.py b/chrome/test/chromedriver/run_buildbot_steps.py
index 45837955f4f13137b221704ba798b4a482393f74..f9a3b47828fadd19567166f631961a6403fe6007 100755
--- a/chrome/test/chromedriver/run_buildbot_steps.py
+++ b/chrome/test/chromedriver/run_buildbot_steps.py
@@ -377,20 +377,6 @@ def _MaybeUpdateLatestRelease(version):
     util.MarkBuildStepError()
 
 
-def _CleanTmpDir():
-  tmp_dir = tempfile.gettempdir()
-  print 'cleaning temp directory:', tmp_dir
-  for file_name in os.listdir(tmp_dir):
-    file_path = os.path.join(tmp_dir, file_name)
-    if file_name.startswith('chromedriver_'):
-      if os.path.isdir(file_path):
-        print 'deleting sub-directory', file_path
-        shutil.rmtree(file_path, True)
-      else:
-        print 'deleting file', file_path
-        os.remove(file_path)
-
-
 def _WaitForLatestSnapshot(commit_position):
   util.MarkBuildStepStart('wait_for_snapshot')
   for attempt in range(0, 200):
@@ -455,15 +441,6 @@ def main():
   if options.android_packages:
     platform = 'android'
 
-  _CleanTmpDir()
-
-  # Make sure any subprocesses (i.e. chromedriver) create temp files under
-  # $TMPDIR/chromedriver_*, so that they can be cleaned up by _CleanTempDir().
-  if util.IsWindows():
-    os.environ['TMP'] = os.environ['TEMP'] = util.MakeTempDir()
-  else:
-    os.environ['TMPDIR'] = util.MakeTempDir()
-
   if not options.revision:
     commit_position = None
   else: