PPC: Support fast-path allocation for subclass constructors with correctly initialized initial maps.

PPC: Support fast-path allocation for subclass constructors with correctly initialized initial maps.

Port b9d25d86a8d57be6184e2610c53c9b8abfd96f11

R=verwaest@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com, dstence@us.ibm.com
BUG=v8:3330
LOG=n

Committed: https://crrev.com/f37269445873218d7de48fed1674e87090e87a56
Cr-Commit-Position: refs/heads/master@{#31926}

[MTBrandyberry, 2015-11-10 19:20:54]

The CQ bit was checked by mbrandy@us.ibm.com to run a CQ dry run

[commit-bot: I haz the power, 2015-11-10 19:20:57]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1434793002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1434793002/1

[commit-bot: I haz the power, 2015-11-10 19:39:56]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-11-10 19:39:57]

Dry run: This issue passed the CQ dry run.

[michael_dawson, 2015-11-10 19:41:43]

On 2015/11/10 19:39:57, commit-bot: I haz the power wrote:
> Dry run: This issue passed the CQ dry run.

lgtm

[MTBrandyberry, 2015-11-10 19:53:24]

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

[commit-bot: I haz the power, 2015-11-10 19:53:30]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1434793002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1434793002/1

[commit-bot: I haz the power, 2015-11-10 19:55:42]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-11-10 19:56:18]

Patchset 1 (id:??) landed as
https://crrev.com/f37269445873218d7de48fed1674e87090e87a56
Cr-Commit-Position: refs/heads/master@{#31926}