Required component for amp-form not detected when invalid <amp-form> is removed from wrapped <form> element

[westonruter]

Bug Description

Given this invalid AMP markup:

<amp-form>
	<form method="GET" id="a_string" class="a_string" action="https://example.com" target="_blank">
		<input type=text value="test" name="hello">
	</form>
</amp-form>

The amp-form is invalid and gets removed, being replaced with its children:

<form method="GET" id="a_string" class="a_string" action="https://example.com" target="_blank">
	<input type="text" value="test" name="hello">
</form>

However, as part of this process the amp-form component script is not being detected as being required for the page.

Originally reported at https://wordpress.org/support/topic/custom-element-scripts-being-removed/

Expected Behaviour

When amp-form > form is on the page, the amp-form component script should be added.

Additional context

• WordPress version: 5.4
• Plugin version: 1.5.1

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Acceptance criteria

Implementation brief

QA testing instructions

Demo

Changelog entry

[amedina]

QA:

• Invalid tag amp-form being removed by the plugin

• amp-form-0.1.js script added

• AMP compatibility preserved

[westonruter]

Build for testing: amp.zip (v1.5.2-RC1-20200403T193031Z-3102c5dea)