Port d4696c48

Original commit message:
This moves the decision whether to report a message or not to when
the pending exception is propagated instead of trying to preserve the
decision in a ThreadLocalTop field.

R=titzer@chromium.org

Review URL: https://codereview.chromium.org/998943003

Cr-Commit-Position: refs/heads/master@{#27150}

R=danno@chromium.org, svenpanne@chromium.org, titzer@chromium.org

BUG=

Review URL: https://codereview.chromium.org/1000963002

Cr-Commit-Position: refs/heads/master@{#27173}