Add finite check to lexer float constants. The fuzzer was generating cases where floating point constants would someone return as valid when they were beyond max float. I was unable to reproduce this in a standalone test, but confirmed this check fixes the fuzzer error. BUG=660702 Change-Id: I9e6b883958013638ea509e38b30e812a9e74fbc1 Reviewed-on: https://chromium-review.googlesource.com/406268 Reviewed-by: Corentin Wallez <cwallez@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>