Track if a non-preprocessor token has been seen and validate #extension with it. 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/267398 Reviewed-by: Zhenyao Mo <zmo@chromium.org> Tested-by: Geoff Lang <geofflang@chromium.org>