Fix flaky idle notification test.

Fix flaky idle notification test.

Idle notification handler might not free more memory if there was a global GC before or incremental marking is not activated (and it's not worth activating).

BUG=
TEST=cctest/test-api/IdleNotificationWithHint

Committed: http://code.google.com/p/v8/source/detail?r=10401

[ulan, 2012-01-13 13:44:24]

Please take a look.

[Erik Corry, 2012-01-13 15:02:21]

I feel like the test is not testing much after this change.  Would making it a
non-threaded test also stop it from being flaky?

[ulan, 2012-01-13 17:06:44]

On 2012/01/13 15:02:21, Erik Corry wrote:
> I feel like the test is not testing much after this change.  Would making it a
> non-threaded test also stop it from being flaky?

I not sure since I cannot reproduce failures locally. They happen only on debug
mac builds.

I uploaded a new patch set which makes the test non-threading and disallows
garbage collection before idle notifications. We could land it and see if it
fixes the problem.

[Erik Corry, 2012-01-14 01:44:53]

LGTM