1519413 - Ensure hit testing works with Fission

Status: RESOLVED DUPLICATE of bug 1519412

(Core :: DOM: UI Events & Focus Handling, enhancement)

Description

[Olli Pettay [:smaug][[e-mail]]]

Attachment: iframe_transform.html example

The initial hit testing which happens outside child processes can be a bit tricky. When an event is got from the OS, it needs to be sent to the right child process (not through topmost child process, since that would leak information and be probably too slow). Perhaps in the simple, and the most common case where iframes are rectangular, Browsing Context Tree could have information about the size and position of the iframes and scroll information could be get from APZ or so.
More complicated case is if iframes are transformed.