It's commented out, as it breaks shader validation in current Chrome :(.
There seems to be some bug in Chrome / ANGLE making it barf when using "gl_FragCoord" in fragment shader.
Curiously, while it breaks both 9.0.576.0 dev channel and latest continuous build 9.0.583.0, it does work fine in canary build with the same version as dev channel (9.0.576.0).
Go figure. Also in Firefox 4 beta 7 it works fine.
It seems there were some recent changes in handling of "gl_FragCoord" on Windows which probably broke something when fixing other bug:
http://code.google.com/p/chromium/issues/detail?id=59762http://code.google.com/p/angleproject/issues/detail?id=71
TODO: make isolated test case and submit bug report (if this doesn't go away in next Chrome update).
Mr.doob
alteredq