This reverts commit f8dc4fb6.

The special state to track field selection is actually necessary to avoid
reduce/reduce conflicts when array constructors are added to the grammar.

BUG=angleproject:941
TEST=WebGL conformance tests, angle_unittests

Change-Id: I55476483c9e83241e8978cd58f05ef303c7c8680
Reviewed-on: https://chromium-review.googlesource.com/260260Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Nicolas Capens <capn@chromium.org>
Tested-by: Olli Etuaho <oetuaho@nvidia.com>