Remove OAuth2TokenServiceRequest

This class exists to enable making access token requests from threads
other than the UI thread. However, it is not used in the codebase, and
it has some amount of maintenance cost and confusion associated with it.
It can always be brought back if needed.

Bug: 967598
Change-Id: I2208d377f852e88f1cd8169202a07ce00d32d53f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1675648
Reviewed-by: Mihai Sardarescu <msarda@chromium.org>
Commit-Queue: Colin Blundell <blundell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#672057}
6 files changed