Fix issue 96, test-debug/ThreadedDebugging is flaky...

Fix issue 96, "test-debug/ThreadedDebugging is flaky"

The previous test assumed the V8 thread would begin executing before the Debugger thread issued its break statement.  Change it so the V8 thread calls its first barrier within the JS infinite loop rather than right before invoking it in the C++ code.  Merged the two JS code snippets into one since the C++ intermediate barrier call was removed.

Ran the test for about 8 hours on Windows without a hang or a failure

BUG=96

[Søren Thygesen Gjesse, 2009-03-27 10:50:38]

Putting a sleep into one test might not seem like a big deal, but with the tests
currently running in 10-12 seconds on a 4 core machine (tools/test.py -j4) it
just takes a few tests with this kind of sleep to degrade that.

You yourself suggested to have the barrier in the JavaScript code as well. I
think that is a good idea. What you need to do is to have a function in
JavaScript that calls back into C++ to wait for the barrier. You can take a look
at CallFunctionInDebugger in test-debug.cc for one example of how to do that or
look at test-api.cc which have a lot of different examples.

http://codereview.chromium.org/42686/diff/1/2
File test/cctest/test-debug.cc (right):

http://codereview.chromium.org/42686/diff/1/2#newcode3383
Line 3383: OS::Sleep(1000);
Please find another way to fix this.

[Matt Hanselman, 2009-04-01 01:58:35]

Apologies for the delay -- I didn't realize I needed to star my own review to
get emails on it.

Agreed putting a barrier in the JS is far better.  I'll run an overnight test on
Windows before submitting the new patch set.

[Matt Hanselman, 2009-04-01 14:00:16]

Reworked to place barrier call in JS code

[Søren Thygesen Gjesse, 2009-04-01 21:05:50]

LGTM

Thank you for the patch Matt. I will put it in Monday.