amp-iframe support of allow-same-origin

[justforfun]

It seems that the support of allow-same-origin atttribute is not working
sandbox="allow-scripts allow-same-origin allow-popups allow-popups-to-escape-sandbox"

This is the error displayed
Origin of must not be equal to container
when on this page
https://justforfun.github.io/examples-amp/article.amp.html
this code is used
<amp-iframe width="300" height="300" sandbox="allow-same-origin allow-popups" layout="responsive" frameborder="0" src="https://justforfun.github.io/examples-amp/video-iframe.html" class="-amp-element -amp-layout-responsive -amp-layout-size-defined -amp-error -amp-layout" id="AMP_7"><i-amp-sizer style="display: block; padding-top: 100%;"></i-amp-sizer> </amp-iframe>

[cramforce]

Right, allow-same-origin is only allowed if the iframe is not on the same origin as the container.

This still allows the iframe to talk to sibling iframes on the same origin.

[cramforce]

Note, that this is not a security invariant. Because AMP files are meant to be distributed via cache domains one cannot expect that the origin would be the same eventually, so this prevents stuff to be working only sometimes.