Make Blink check the Chromium-side spellcheck-enabled status

We currently maintain two spellcheck-enabled status, one in Blink
and one in Chromium. This patch makes the Chromium-side status the
only effective one, by changing all querying of the Blink-side status
to query the Chromium-side one instead. In this way, we reduce
maintenance cost, and also fix a bug in syncing the the two statuses
(regression test included).

After this patch, the Blink-side status becomes useless. A follow-up
patch (crrev.com/c/827558) will remove it and its relevant dead code.

Bug: 789273, 710097
Change-Id: I5d4ee851934a3cb2139f0df9aa4df949071644a6
Reviewed-on: https://chromium-review.googlesource.com/821496
Reviewed-by: Rachel Blum <groby@chromium.org>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Reviewed-by: Emil A Eklund <eae@chromium.org>
Reviewed-by: Alex Moshchuk <alexmos@chromium.org>
Commit-Queue: Xiaocheng Hu <xiaochengh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#525157}
14 files changed