GitLab

This CL makes URLFetcherFileWriter::Finish() skip closing file when there is an
error. If there is an error, Finish() will delete the file after any pending
operation completes.

TBR=hashimoto@chromium.org
TBR=mkwst@chromium.org
BUG=487732, 656692

Review-Url: https://chromiumcodereview.appspot.com/2425673006
Cr-Commit-Position: refs/heads/master@{#426540}