[builtins] Get rid of a few %_ClassOf uses.

[builtins] Get rid of a few %_ClassOf uses.

With subclassing and @@toStringTag, %_ClassOf is not necessarily what
you want for ES6 anymore, so better avoid relying on %_ClassOf in our
builtins.

R=yangguo@chromium.org

Committed: https://crrev.com/dd0ba4d1320ab44500f79331fd9cd5f0f275dc34
Cr-Commit-Position: refs/heads/master@{#31953}

[Benedikt Meurer, 2015-11-12 08:15:09]

Hey Yang,

This is some trivial cleanup.
Please take a look.

Thanks,
Benedikt

[Yang, 2015-11-12 08:15:13]

On 2015/11/12 08:13:46, Benedikt Meurer wrote:

lgtm

[Benedikt Meurer, 2015-11-12 08:15:21]

The CQ bit was checked by bmeurer@chromium.org

[commit-bot: I haz the power, 2015-11-12 08:15:26]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1439003002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1439003002/1

[commit-bot: I haz the power, 2015-11-12 08:33:39]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-11-14 23:20:26]

Patchset 1 (id:??) landed as
https://crrev.com/dd0ba4d1320ab44500f79331fd9cd5f0f275dc34
Cr-Commit-Position: refs/heads/master@{#31953}