Fix a bug in init_varyings_without_static_use workaround. 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/197294 Reviewed-by: Kenneth Russell <kbr@chromium.org> Reviewed-by: Shannon Woods <shannonwoods@chromium.org> Tested-by: Zhenyao Mo <zmo@chromium.org>