Split files into worker and main thread pieces.
Show sensible output for showText commands in the stepper.
Don't provide optional pushState parameter
Merge pull request #3530 from brendandahl/worker-split

Split files into worker and main thread pieces.
Merge remote-tracking branch 'mozilla/master' into pushState
IE9 does not need onreadystatechange
Merge pull request #3581 from yurydelendik/pushState

Misc IE fixes
Merge pull request #3575 from brendandahl/text-debugger

Show sensible output for showText commands in the stepper.