Remove unnecessary call to StoragePartition::GetURLRequestContext in ArcAuthContext.

It didn't actually use the return value anymore (after conversion to SimpleURLLoader in r610189),
so just return a boolean.

Bug: 837753
Change-Id: I9712f1520db8203f821e36c738c290c783d97dbe
Reviewed-on: https://chromium-review.googlesource.com/c/1372913
Reviewed-by: Yury Khmel <khmel@chromium.org>
Commit-Queue: John Abd-El-Malek <jam@chromium.org>
Cr-Commit-Position: refs/heads/master@{#615809}
4 files changed