GitLab

APIBindingBridge calls back into JS to allow custom JS bindings to
register any hooks needed. Check context validity before executing
JS, and gracefully throw an error if the context is invalid.

Add unittests for the same.

Bug: 819968

Change-Id: Ibb724537c4bf3d320a6f4a80b9f19fe413e00840
Reviewed-on: https://chromium-review.googlesource.com/958296Reviewed-by: Jeremy Roman <jbroman@chromium.org>
Commit-Queue: Devlin <rdevlin.cronin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#543332}