Revert of Do not scan the active part of the stack in oilpan conservative garbage collections.

Revert of Do not scan the active part of the stack in oilpan conservative garbage collections. (https://codereview.chromium.org/152513006/)

Reason for revert:
Caused http/tests/workers/terminate-during-sync-operation.html to crash. 

http://test-results.appspot.com/dashboards/flakiness_dashboard.html#group=%40ToT%20Blink&tests=http%2Ftests%2Fworkers%2Fterminate-during-sync-operation.html


Original issue's description:
> Do not scan the active part of the stack in oilpan conservative garbage collections.
> 
> If threads are allowed to continue after safepointing there is a
> stack marker. We should stop stack scanning at the marker in that
> case. If there is no marker the thread whose thread we are iterating
> will be blocked and we should scan all the way to the recorded
> end stack pointer.
> 
> R=vegorov@chromium.org
> BUG=
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=166634

TBR=vegorov@chromium.org,haraken@chromium.org,wibling@chromium.org,ager@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=166720

[abarth-chromium, 2014-02-07 16:40:37]

Created Revert of Do not scan the active part of the stack in oilpan
conservative garbage collections.

[commit-bot: I haz the power, 2014-02-07 16:41:00]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/abarth@chromium.org/157593004/1

[commit-bot: I haz the power, 2014-02-07 16:41:44]

Change committed as 166720