Fix sporadic crash in the RequestInterruptTestWithNativeAccessor.

The test was broken. V8 currently does not correctly lookup NativeDataProperty accessors attached to the PrototypeTemplate of FunctionTemplate (Issue 3066). As the result while(obj.shouldContinue) loop was immediately exiting and the test would terminate while RequestInterruptTestBase::InterruptThread would be still starting up. As the result later InterruptThread would try to access members of the test object which was destroyed.

The test was fixed:

- instead of attaching accessor to PrototypeTemplate we attach it to  InstanceTemplate;
- an assertion was added to verify that we completed the test successfully due to interruptor firing not due to sporadic loop termination due to some unrelated bug.

R=hpayer@chromium.org

Review URL: https://codereview.chromium.org/109653010

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@18391 ce2b1a6d-e550-0410-aec6-3dcde31c8c00