Double the API call rate threshold for the memory reducer to kick in

Double the API call rate threshold for the memory reducer to kick in

Moving Blink from hidden values to private symbols almost doubled the
rate of API calls, as the private symbols API increases the call-depth
scope while the hidden values one didn't.

I manually checked that this fixes the regression on the long running
gmail benchmark but doesn't add new memory reducer GCs on the infinite
scrolling benchmark

BUG=chromium:561325
R=ulan@chromium.org
LOG=n

Committed: https://crrev.com/9ec240d00cb8c59a33005accab1151ca3b741638
Cr-Commit-Position: refs/heads/master@{#32279}

[ulan, 2015-11-25 14:05:31]

lgtm

[jochen (gone - plz use gerrit), 2015-11-25 14:06:43]

The CQ bit was checked by jochen@chromium.org

[commit-bot: I haz the power, 2015-11-25 14:06:53]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1472193003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1472193003/1

[commit-bot: I haz the power, 2015-11-25 15:20:09]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-11-25 15:20:22]

Patchset 1 (id:??) landed as
https://crrev.com/9ec240d00cb8c59a33005accab1151ca3b741638
Cr-Commit-Position: refs/heads/master@{#32279}