ANGLE used to accept shaders with non-sized arrays in initializer lists.
Fix this. Proper support for implicitly sized arrays will be implemented
later for ESSL3.

TEST=angle_unittests
BUG=angleproject:941

Change-Id: I53c5ccf0f7ef09ad30e142f8350812959fc4846c
Reviewed-on: https://chromium-review.googlesource.com/264360Tested-by: Olli Etuaho <oetuaho@nvidia.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>