The motivation for this is that it greatly reduces the RelocInfo size.
This also results in a small improvement in compile time.

Note: This CL was based on https://codereview.chromium.org/2651833003,
and basically reverts that CL (but handles code changes and some
minor bugs in previous code).

Bug: chromium:772780
Change-Id: I55dd48d3bddd4b3d1c8eec13791b3ee4c485c604
Reviewed-on: https://chromium-review.googlesource.com/730649Reviewed-by: Mircea Trofin <mtrofin@chromium.org>
Reviewed-by: Eric Holk <eholk@chromium.org>
Commit-Queue: Karl Schimpf <kschimpf@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48947}