Also clear the stamp file if the download file or extracted directory goes missing.

third_party/binutils/download.py

 #!/usr/bin/env python
 # Copyright 2014 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.
 # vim: set ts=2 sw=2 et sts=2 ai:
 
 """Minimal tool to download binutils from Google storage.
 
 TODO(mithro): Replace with generic download_and_extract tool.
 """
@@ skipping 46 matching lines @@
 
   sha1file = tarball + '.sha1'
   if not os.path.exists(sha1file):
     print "WARNING: No binutils found for your architecture (%s)!" % GetArch()
     return 0
 
   checksum = ReadFile(sha1file)
 
   stampfile = tarball + '.stamp'
   if os.path.exists(stampfile):
-    if checksum == ReadFile(stampfile):
+    if (os.path.exists(tarball) and
+        os.path.exists(outdir) and
+        checksum == ReadFile(stampfile)):
       return 0
     else:
       os.unlink(stampfile)
 
   print "Downloading", tarball
   subprocess.check_call([
       'download_from_google_storage',
       '--no_resume',
       '--no_auth',
       '--bucket', 'chromium-binutils',
@@ skipping 11 matching lines @@
 
   for tool in BINUTILS_TOOLS:
     assert os.path.exists(os.path.join(outdir, tool))
 
   WriteFile(stampfile, checksum)
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv))