Fix test crashes by doing an additional GC on cleanup.

Source/heap/ThreadState.cpp

Index: Source/heap/ThreadState.cpp
diff --git a/Source/heap/ThreadState.cpp b/Source/heap/ThreadState.cpp
index 4bd7a10b5e29644b1ba2894aee1a793d2309d9a0..935284cec6aff4ce5b627ded3b13a9475cdd2d99 100644
--- a/Source/heap/ThreadState.cpp
+++ b/Source/heap/ThreadState.cpp
@@ -298,6 +298,12 @@ void ThreadState::cleanup()
     // After this GC we expect heap to be empty because
     // preCleanup tasks should have cleared all persistent
     // handles that were externally owned.
+    // FIXME: oilpan: we should perform a single GC and everything
+    // should die. Unfortunately it is not the case for all objects
+    // because the hierarchy was not completely moved to the heap and
+    // some heap allocated objects own objects that contain persistents
+    // pointing to other heap allocated objects.
+    Heap::collectGarbage(ThreadState::NoHeapPointersOnStack);
     Heap::collectGarbage(ThreadState::NoHeapPointersOnStack);
 
     // Verify that all heaps are empty now.