Precision emulation rounding function calls and vector/matrix dynamic
indexing function calls now get a flag that indicates that running the
function body does not have side effects. This avoids triggering
asserts in OutputHLSL when these internal function calls end up on the
right hand side of a non-unfolded logical operator.

BUG=chromium:724870
TEST=angle_unittests

Change-Id: Id1a2b6b744f6a04c6cdb86a8f4109ccc12bc70b9
Reviewed-on: https://chromium-review.googlesource.com/516705Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>