This shows an improvement in the code size of the bytecode handlers.
When a range is split (because for example the preferred register gets
clobbered by a call and is not available for the whole range), trying
to allocate the preferred register for the first range that results
from the split avoids some extra register moves.

BUG=

Review-Url: https://codereview.chromium.org/2749023005
Cr-Commit-Position: refs/heads/master@{#43905}