Add integration test for shadow dom

[jpettitt]

We've had multiple issues with DOM inconsistencies when AMP code is imported through a shadow dom based mechanism (in Polymer ), see list below. We need some shadow dom integration tests.

Here some of the issues:
#19434 amp-experiment
#19694 amp-subscriptions-google
#12912 amp-ads
#12388 amp-img
#12151 amp-list
#10799 amp-access

[justforfun]

Here is another one:
#20008

[justforfun]

We a brand new issue of the same kind:
#20400

[jpettitt]

Is this on the roadmap?

cc @rudygalfi

[rudygalfi]

@rsimha let us know your thoughts here.

[rsimha]

I think this can be covered by E2E tests now. @prateekbh Can you comment?

[prateekbh]

Yes, I had a conversation around the same and definitely looks like this can be done via e2e tests

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed in 7 days if no further activity occurs. Thank you for your contributions.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed in 7 days if no further activity occurs. Thank you for your contributions.