servo/servo — pull request #3197 by mrobinson (2014-09-02 18:55:01+00:00)
Title: Better handling of iframes in the compositor tree

This is a rework of Brian Bell's original PR from https://github.com/mrobinson/servo/commit/6fd3dc5d0fe61afcb50592382006a607d88cdee8. It splits his one commit into independent pieces, preserves the existing "root layer + base layer" compositor tree layout, and includes miscellaneous other cleanup.