Port 2b9112a5

Original commit message:
This optimization is already implemented in fullcodegen, and
basically makes sure that we do not unecessarily blow up the
code with duplicated return sequences everywhere.

R=bmeurer@chromium.org, dstence@us.ibm.com, michael_dawson@ca.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1218493003

Cr-Commit-Position: refs/heads/master@{#29333}