PPC: [builtins] One runtime fallback is enough for the String constructor.

PPC: [builtins] One runtime fallback is enough for the String constructor.

Port 34b7b21d1d7bf2e9c77ae5726f868e69f3b4a4f3

Original commit message:
    If inline allocation fails, we can just use the %NewObject fallback,
    which will do the right thing. We don't need a dedicated fallback to
    %AllocateInNewSpace.

R=bmeurer@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=

Committed: https://crrev.com/ff4c3f31a0cbf450d33b551b21b9ba295feab815
Cr-Commit-Position: refs/heads/master@{#32015}

[JoranSiu, 2015-11-16 15:59:12]

lgtm

[MTBrandyberry, 2015-11-16 16:11:52]

The CQ bit was checked by mbrandy@us.ibm.com

[commit-bot: I haz the power, 2015-11-16 16:11:56]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1448063002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1448063002/1

[commit-bot: I haz the power, 2015-11-16 16:53:43]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-11-16 16:54:09]

Patchset 1 (id:??) landed as
https://crrev.com/ff4c3f31a0cbf450d33b551b21b9ba295feab815
Cr-Commit-Position: refs/heads/master@{#32015}