[turbofan] Canonicalize return sequence for JSFunctions.

[turbofan] Canonicalize return sequence for JSFunctions.

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=danno@chromium.org

Committed: https://crrev.com/2b9112a578f66fc976557aededf3e203f48c395e
Cr-Commit-Position: refs/heads/master@{#29315}

[Benedikt Meurer, 2015-06-26 08:47:27]

Hey Danno,

This is the optimization we just talked about. Please take a look.

Thanks,
Benedikt

[Jarin, 2015-06-26 09:19:22]

jarin@chromium.org changed reviewers:
+ jarin@chromium.org

[Jarin, 2015-06-26 09:19:23]

lgtm

[Jarin, 2015-06-26 09:19:27]

The CQ bit was checked by jarin@chromium.org

[commit-bot: I haz the power, 2015-06-26 09:19:33]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1211373002/1

[commit-bot: I haz the power, 2015-06-26 09:34:37]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-06-26 09:34:56]

Patchset 1 (id:??) landed as
https://crrev.com/2b9112a578f66fc976557aededf3e203f48c395e
Cr-Commit-Position: refs/heads/master@{#29315}