The TType constrcuted is using es2 signature, which is different from the es3 signature.

BUG=angle:568
TEST=webgl conformance tests with --init_varyings_without_static_use commandline switch

Change-Id: I15347c7a6fe67e9214e4c96b156a50806a90c97c
Reviewed-on: https://chromium-review.googlesource.com/197294Reviewed-by: Kenneth Russell <kbr@chromium.org>
Reviewed-by: Shannon Woods <shannonwoods@chromium.org>
Tested-by: Zhenyao Mo <zmo@chromium.org>