Tested with GLSL ES conformance suite (which doesn't test this) and
the WebGL conformance suite, which now contains tests to ensure that
these constructs compile correctly.

Chromium bug: http://crbug.com/86952
Review URL: http://codereview.appspot.com/4897045

git-svn-id: https://angleproject.googlecode.com/svn/trunk@731 736b8ea6-26fd-11df-bfd4-992fa37f6226