Define simple accessors in the header and give them lower case names.

R=mstarzinger@chromium.org

Bug: v8:7570
Change-Id: I2914013fdea2218189275bbaa9f98ea5de0ccd7c
Reviewed-on: https://chromium-review.googlesource.com/1046546
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53024}