improve web benchmark error reporting

[yjbanov]

Description

• Aggressively stop benchmarks in the presence of errors
• Forward errors to localhost for forwarding to test results
• Wrap the checkbox in Material and Directionality. Otherwise it fails assertions in debug mode (probably for good reason). This was not noticed in benchmarks because we don't run them in debug mode.

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[mdebbar]

Instead of checking for _hasErrored in multiple places, what if we check for it in _shouldContinue() and rely on existing logic to stop pumping frames?

[yjbanov]

I can't think of a clean way to use it. Currently _shouldContinue depends on everything being healthy. For example, it extracts the profile from rendered frames. It only communicates two signals: "continue running" and "benchmark finished successfully". We'd have to add a third value communicating "benchmark errored and must halt". When an error happens the system could be in a corrupted state, in which case our job is to halt immediately and report the error before it's obscured by something else. IOW I think they have sufficiently different roles to warrant separate codepaths and separate signals.

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[mdebbar]

LGTM