On Android we have until now determined the compositor widget's size
by querying the values from the ANativeWindow. However, since bug
1780093 landed we can now switch between which Surface we are
rendering in to, and as a result we appear to be using the wrong size
some of the time.
This patch is a speculative attempt to fix this, by using the size
passed to ResumeAndResize() (which itself comes from the Surface's
surfaceChanged() callback) rather than querying the window.
Differential Revision: https://phabricator.services.mozilla.com/D154909