[turbofan] Treat PREMONOMORPHIC like UNINITIALIZED.

[turbofan] Treat PREMONOMORPHIC like UNINITIALIZED.

When a (Keyed)Load/StoreIC reports PREMONOMORPHIC, just treat it like
UNINITIALIZED for now and add a soft deoptimization exit.

R=mvstanton@chromium.org
BUG=v8:5267

[Benedikt Meurer, 2016-09-06 09:57:30]

The CQ bit was checked by bmeurer@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-09-06 09:57:37]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-09-06 10:16:05]

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

[commit-bot: I haz the power, 2016-09-06 10:16:06]

Dry run: Try jobs failed on following builders:
  v8_linux64_asan_rel_ng on master.tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_linux64_asan_rel_ng/buil...)
  v8_linux64_asan_rel_ng_triggered on master.tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_linux64_asan_rel_ng_trig...)

[mvstanton, 2016-09-06 10:42:12]

LGTM.

[Benedikt Meurer, 2016-09-06 10:43:40]

The CQ bit was checked by bmeurer@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-09-06 10:43:47]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-09-06 11:06:55]

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

[commit-bot: I haz the power, 2016-09-06 11:06:55]

Dry run: This issue passed the CQ dry run.