GitLab

When the Dice token exchange fails:
- if this is a Sync signin, the tab is navigated to the NTP, to match
  the behavior of the success case
- if this is a Sync signin or if Dice is fully enabled for this profile,
  display the signin error dialog.

Bug: 789130
Change-Id: I4a5309a18301c4e3112db50296edd625682f0fd3
Reviewed-on: https://chromium-review.googlesource.com/810805
Commit-Queue: David Roger <droger@chromium.org>
Reviewed-by: Mihai Sardarescu <msarda@chromium.org>
Cr-Commit-Position: refs/heads/master@{#522416}