Condition calculation in for and while loops has bug on Intel Mac. Work
around it by converting "CONDITION" to "CONDITION && true".

This CL also adds previous SH_EMULATE_ABS_INT_FUNCTION workaround to
the ANGLE GL back-end on OSX

BUG=chromium:644669
TEST=deqp/functional/gles3/shaderloop_for/while.html

Change-Id: I910f662b054f259fcb601b9938841b3a2d066840
Reviewed-on: https://chromium-review.googlesource.com/381678Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Qiankun Miao <qiankun.miao@intel.com>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>