Dampen the old generation allocation limit only after the initial old generation size was configure…

Dampen the old generation allocation limit only after the initial old generation size was configured.

Otherwise, dampening interferes with initial size configuration and causes GC too early.

BUG=501703
LOG=NO

Committed: https://crrev.com/42263aab992b52d8eb5bfdc99fcbcadb4915aa36
Cr-Commit-Position: refs/heads/master@{#29106}

[ulan, 2015-06-18 09:04:58]

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

[ulan, 2015-06-18 09:05:06]

PTAL

[jochen (gone - plz use gerrit), 2015-06-18 09:12:51]

lgtm

[ulan, 2015-06-18 09:33:01]

The CQ bit was checked by ulan@chromium.org

[commit-bot: I haz the power, 2015-06-18 09:33:18]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1183633005/1

[commit-bot: I haz the power, 2015-06-18 10:00:18]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-06-18 10:00:35]

Patchset 1 (id:??) landed as
https://crrev.com/42263aab992b52d8eb5bfdc99fcbcadb4915aa36
Cr-Commit-Position: refs/heads/master@{#29106}