Fix flakiness of optimization assertion on slow ARM builders

(if the test ran too slow, optimization kicked in earlier than expected by the test)

TEST=mjsunit/assert-opt-and-deopt.js no longer flaky

Review URL: http://codereview.chromium.org/7298001

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8511 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

test/mjsunit/assert-opt-and-deopt.js

@@ -148,7 +148,7 @@ tracker.AssertIsOptimized(f, false);
 tracker.AssertDeoptHappened(f, false);
 tracker.AssertDeoptCount(f, 0);
 
-for (var i = 0; i < 5; i++) f(1);
+for (var i = 0; i < 2; i++) f(1);
 
 tracker.AssertOptCount(f, 0);
 tracker.AssertIsOptimized(f, false);