Relax test constraints from r15439 (Join threads after stopping).

R=hpayer@chromium.org
BUG=

Review URL: https://codereview.chromium.org/18509002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15440 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

test/cctest/test-mark-compact.cc

@@ -581,9 +581,9 @@ intptr_t ShortLivingIsolate() {
 
 
 TEST(RegressJoinThreadsOnIsolateDeinit) {
-  intptr_t first_size = ShortLivingIsolate();
+  intptr_t size_limit = ShortLivingIsolate() * 2;
   for (int i = 0; i < 10; i++) {
-    CHECK_EQ(first_size, ShortLivingIsolate());
+    CHECK_GT(size_limit, ShortLivingIsolate());
   }
 }