Collect phantom callback data only once during gc. For scavenges, just consider the young handles r…

Collect phantom callback data only once during gc. For scavenges, just consider the young handles referenced by young generation.

BUG=

Committed: https://crrev.com/9b60e894828532a22b272502128de870b36a6aa7
Cr-Commit-Position: refs/heads/master@{#26344}

[Hannes Payer (out of office), 2015-01-29 21:00:44]

hpayer@chromium.org changed reviewers:
+ jochen@chromium.org, ulan@chromium.org

[jochen (gone - plz use gerrit), 2015-01-30 08:14:59]

lgtm

[Hannes Payer (out of office), 2015-01-30 08:21:00]

The CQ bit was checked by hpayer@chromium.org

[commit-bot: I haz the power, 2015-01-30 08:21:28]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/885553005/1

[commit-bot: I haz the power, 2015-01-30 08:22:59]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-01-30 08:23:19]

Patchset 1 (id:??) landed as
https://crrev.com/9b60e894828532a22b272502128de870b36a6aa7
Cr-Commit-Position: refs/heads/master@{#26344}