Recompute compositing geometry state after a WebGL context is restored after being lost.

This behavior was lost by crrev.com/177203007, which also removed a bunch of work that breaks chicken-egg compositing ordering in Blink. This CL re-adds only the necessary compositing dirty bit, and so does not reintroduce the chicken-egg issue.

BUG=349195

Review URL: https://codereview.chromium.org/184273008

git-svn-id: svn://svn.chromium.org/blink/trunk@168870 bbb929c8-8fbe-4397-9dbb-9b2b20218538