GitLab

These were writing to the current user's downloads directory instead of
a unique temporary directory.

BUG=372017
R=asargent@chromium.org, jamescook@chromium.org
TBR=asargent

Review URL: https://codereview.chromium.org/276133002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@269538 0039d316-1c4b-4281-b951-d872f2087c98