Fixes:
dEQP-GLES2.functional.shaders.preprocessor.extensions.after_non_preprocessing_tokens_vertex
dEQP-GLES2.functional.shaders.preprocessor.extensions.after_non_preprocessing_tokens_fragment

BUG=angleproject:989

Change-Id: Ie0aba80b2fde0160e83fc95f545b62954af2e5fc
Reviewed-on: https://chromium-review.googlesource.com/267398Reviewed-by: Zhenyao Mo <zmo@chromium.org>
Tested-by: Geoff Lang <geofflang@chromium.org>