Fix ExtensionsRegistration cctest on ARM.

Fix ExtensionsRegistration cctest on ARM.
Reduced the number of created threads on ARM.

Committed: http://code.google.com/p/v8/source/detail?r=10045

[Dmitry Lomov (no reviews), 2011-11-22 18:36:16]

Limited the number of threads for ARM.

[Rico, 2011-11-22 18:40:39]

LGTM, do we need the distinction? is this a regression test that uncovers
something by having 40 isolates? Or is 10 enough for the other platforms as
well?

[Dmitry Lomov (no reviews), 2011-11-22 18:47:50]

On 2011/11/22 18:40:39, Rico wrote:
> LGTM, do we need the distinction? is this a regression test that uncovers
> something by having 40 isolates? Or is 10 enough for the other platforms as
> well?

40-50 was enough on Linux to fail every time (before the bug was fixed).
10 was flaky on Linux (fails every 2nd-3rd run).
Threading tests like this are inherently flaky - the more of everything you
have, the less the possibility that test avoids uncovering a bug)

[Rico, 2011-11-22 18:50:36]

In that case, LGTM :-)