Validate in-process plugin instance messages.

Bug: 733548, 733549
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_site_isolation
Change-Id: Ie5572c7bcafa05399b09c44425ddd5ce9b9e4cba
Reviewed-on: https://chromium-review.googlesource.com/538908
Commit-Queue: Bill Budge <bbudge@chromium.org>
Reviewed-by: Raymes Khoury <raymes@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#480696}
Review-Url: https://codereview.chromium.org/2955703002 .
Cr-Commit-Position: refs/branch-heads/3112@{#456}
Cr-Branched-From: b6460e24cf59f429d69de255538d0fc7a425ccf9-refs/heads/master@{#474897}
2 files changed