This is a step towards having Blink no longer look directly at the
line endings array.  That prevented https://codereview.chromium.org/1137683003/
from landing.  Next step, after the roll, will be using these
functions in Blink.
R=jochen@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1213783002

Cr-Commit-Position: refs/heads/master@{#29330}