Use sequence checker in chrome_mojo_proxy_resolver_factory.

The ChromeMojoProxyResolverFactory may be created in early startup when the ui
thread hasn't be promoted to BrowserThread::UI. Therefore, it can't use
DCHECK_CURRENTLY_ON(content::BrowserThread::UI) to check whether it is accessed
on the same thread. Instead, we could use SequenceCheck for the check and make
sure it is accessed sequentially.

Bug: 729596
Change-Id: Id31e53e1ec369b029a843656cf86fc605d768a43
Reviewed-on: https://chromium-review.googlesource.com/c/1308667
Reviewed-by: Matt Menke <mmenke@chromium.org>
Commit-Queue: Xi Han <hanxi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#604404}
2 files changed