fix getActiveMap
Merge pull request #241 from greggman/fix-webgl-test-utils

fix getActiveMap
add getPrefixedProperty
add fullscreen utilities
add test that framebuffers don't lose content when switching in/out of fullscreen
Merge pull request #242 from greggman/add-fullscreen-test

Add fullscreen test
update framebuffers-keep-contents-exiting-fullscreen-mode

Keep the red rectanlge at all times. Add explanation
Merge pull request #243 from greggman/update-framebuffers-keep-contents-exiting-fullscreen-mode

update framebuffers-keep-contents-exiting-fullscreen-mode