Allow applying preload scripts to opened contexts

[OrKoN]

This change allows specifying that a specific preload script should apply not only to the specified contexts and but also to all contexts opened by the specified contexts (recursively).

Issue #756

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[whimboo]

This needs new tests as well, right?

[css-meeting-bot]

The Browser Testing and Tools Working Group just discussed Allow applying preload scripts to opened contexts.

The full IRC log of that discussion

<AutomatedTester> topic: Allow applying preload scripts to opened contexts
<AutomatedTester> github: https://github.com//pull/803
<AutomatedTester> orkon: this is one of the. topics that was brought up by the playwright folks
<jgraham> q+
<AutomatedTester> ... this is the PR that prepared to implements inheritance for preload scripts
<sadym> q+
<AutomatedTester> ... I wonder if there are concerns with this approach and would this have an issue with the events being sent out?
<AutomatedTester> ack next
<AutomatedTester> jgraham: I think we shouild do this
<AutomatedTester> ... we should be looking to add global configuration or top level traversibles be documented
<AutomatedTester> ... I agree we should be doing this but I think we need to be aware of all the different ways that we should bve doing this
<AutomatedTester> q?
<AutomatedTester> ack next
<AutomatedTester> sadym: this looks like a new mechanism. I wonder if this playwright appraoch could not be handled with using preload script globally
<AutomatedTester> jgraham: I think it could but that might be harder
<AutomatedTester> ... people would want it a per context and I think we want it inheritable. They are both required
<AutomatedTester> q?