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Listeners can throw exceptions (as with any third-party code). Ensure
that we have tests for this. When a listener throws an exception, it
should be logged to the console, but not bubbled up to external try-
catches (so that JS code that may have triggered the event doesn't
receive it). This is the same as we do for web events.

BUG=653596

Review-Url: https://codereview.chromium.org/2613093002
Cr-Commit-Position: refs/heads/master@{#442759}