Post-surfman issues

[jdm]

Issues that aren't important enough to block merging surfman but we should make a point of coming back to investigate after the merge:

• simple babylon demo renders a white screen in the glwindow immersive backend (http://paulrouget.com/test/bbjs/basic/)
• a number of threejs webvr examples don't show content in immersive mode; verify pre-surfman behaviour here (http://rawcdn.githack.com/mrdoob/three.js/r105/examples/webvr_sandbox.html)

[jdm]

These were addressed.