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

test/cctest/test-mark-compact.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
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@@ skipping 563 matching lines @@
     v8::HandleScope handle_scope;
     v8::Local<v8::Context> context = v8::Context::New(isolate);
     CHECK(!context.IsEmpty());
   }
   isolate->Dispose();
   return MemoryInUse();
 }
 
 
 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());
   }
 }
 
 #endif  // __linux__ and !USE_SIMULATOR