preprocessor: add a limit to the number of token expanded BUG=angleproject:1522 BUG=chromium:648074 Change-Id: Ibf0858aaeb81933dd221ac82a49160169b48a495 Reviewed-on: https://chromium-review.googlesource.com/387211 Reviewed-by: Geoff Lang <geofflang@chromium.org> Commit-Queue: Corentin Wallez <cwallez@chromium.org>