Without this change, the extracted directory could be missing but
the downloaded file could match the hash, and in turn
download_from_google_storage will not download the file and will
not extract it, and any tools depending on the extracted
directory will fail.

Review URL: https://codereview.chromium.org/1904483002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@300051 0039d316-1c4b-4281-b951-d872f2087c98