Update extensions downloads API incognito profile access.

Download function of Extensions Downloads API used incognito downnload
manager, if available, even if the request was from regular profile.

This is changed to using the download manager of current profile.

Bug: 845845
Change-Id: I751a06850f0c9d6ac288ec9ff83bc592012fc3f5
Reviewed-on: https://chromium-review.googlesource.com/1087963
Commit-Queue: Ramin Halavati <[email protected]>
Reviewed-by: Ben Hayden <[email protected]>
Reviewed-by: David Trainor <[email protected]>
Cr-Commit-Position: refs/heads/master@{#565941}
3 files changed