Populate PrototypeInfo with prototype_object value

Populate PrototypeInfo with prototype_object value

But only if --track-prototype-users, which is still off by default.
This is the next step towards prototype chain check elimination.

[Jakob Kummerow, 2015-03-24 13:56:29]

jkummerow@chromium.org changed reviewers:
+ verwaest@chromium.org

[Jakob Kummerow, 2015-03-24 13:56:29]

Another piece of https://codereview.chromium.org/908213002/ that can be reviewed
on its own. PTAL.

[Jakob Kummerow, 2015-03-31 18:49:46]

On 2015/03/24 13:56:29, Jakob wrote:
> Another piece of https://codereview.chromium.org/908213002/ that can be
reviewed
> on its own. PTAL.

As discussed, we don't need this any more. Closing.