Failing test in angle_end2end_tests:

GLSLTest.MaxMinusTwoVaryingVec4PlusTwoSpecialVariables:
program link failed: C:\fakepath(87,5-18): error X4000: variable 'output' used without having been completely initialized

This reverts commit 73e32ee1.

Change-Id: Ie47cb3a92ccfa1271a880a8b7e5a87b05963bab9
Reviewed-on: https://chromium-review.googlesource.com/305530Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>