#474 Add ability to copy text out of an iframe or closed shadow DOM within the remote page

[Anonymous]

Originally created by: 00000o1

• iframe: this will be easy. we can just use an injected script into the iframe in the remote page within the browser context
• closed shadow DOM: this will require using the flattened document tree from the protocol backend and will be a bit tricky.

Overall the different approaches could be used side by side or it might make more sense to shift everything to the more general: flattened document tree approach.

Performance is not an issue as copy events are not something that occurs in high frequency, they are just "human UI frequency" so even if we have to do an expensive processing of a flattened document tree, it's completely acceptable