[download] DownloadTest.Resumption_Automatic should check final path.

Automatic resumption stresses the download target determination in ways
that regular resumption doesn't. Add a check for Resumption_Automatic
test to verify that the correct target path is determined.

R=svaldez@chromium.org
BUG=7648

Review URL: https://codereview.chromium.org/1549573002

Cr-Commit-Position: refs/heads/master@{#366664}
1 file changed