GitLab

Replace current ThreadId check with a sequence checker.

We also add a test that tests font fallback, so
PpapiBlinkPlatformImpl::SandboxSupport::GetFallbackFontForCharacter
actually gets tested somewhere.

Bug: 866645
Change-Id: I743eb9cd6a1004c25074b907a50e9b4cf680f805
Reviewed-on: https://chromium-review.googlesource.com/1165312Reviewed-by: Bill Budge <bbudge@chromium.org>
Reviewed-by: Gabriel Charette <gab@chromium.org>
Reviewed-by: Antoine Labour <piman@chromium.org>
Commit-Queue: Fernando Serboncini <fserb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#581302}