[turbofan] Add support for keyed access to named properties.

[turbofan] Add support for keyed access to named properties.

The compiler can generate a named access for o[x] if x is a compile time
constant that can be turned into a name using ToName (limited to
primitive x values, because other ToName invocations might be observable),
or the KeyedLoadIC/KeyedStoreIC have gather constant name feedback for x
(i.e. the access always goes to the same symbol).

R=jarin@chromium.org
BUG=v8:4470
LOG=n

Committed: https://crrev.com/7fcad712ed65ef2811944ef8902106f675956cd5
Cr-Commit-Position: refs/heads/master@{#31703}

[Benedikt Meurer, 2015-11-02 08:28:41]

Hey Jaro,

Initial keyed access support for named properties.
Please take a look.

Thanks,
Benedikt

[Jarin, 2015-11-02 08:53:11]

lgtm

[Benedikt Meurer, 2015-11-02 08:53:25]

The CQ bit was checked by bmeurer@chromium.org

[commit-bot: I haz the power, 2015-11-02 08:53:41]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1414013004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1414013004/1

[commit-bot: I haz the power, 2015-11-02 08:55:07]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-11-02 08:55:25]

Patchset 1 (id:??) landed as
https://crrev.com/7fcad712ed65ef2811944ef8902106f675956cd5
Cr-Commit-Position: refs/heads/master@{#31703}