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..ce8db96a036260fa390aec3090da0bf9198a3495 100644
--- a/Source/heap/ThreadState.cpp
+++ b/Source/heap/ThreadState.cpp
@@ -298,6 +298,8 @@ 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: get rid of the additional GC.

[haraken, 2014/02/27 11:30:31]

Just help me understand: Why is this a FIXME? I guess that we need to call
multiple GCs to break persistent chains.

[Vyacheslav Egorov (Chromium), 2014/02/27 11:32:26]

Because in the end everything will be moved to the heap and persistents will
disappear.

[haraken, 2014/02/27 11:37:20]

I'm not sure how realistic it is. We'll anyway have off-heap and on-heap, and
will have a pointer from off-heap to on-heap (which is persistent).

+    Heap::collectGarbage(ThreadState::NoHeapPointersOnStack);
     Heap::collectGarbage(ThreadState::NoHeapPointersOnStack);

[haraken, 2014/02/27 11:30:31]

Are two GCs enough?

[Vyacheslav Egorov (Chromium), 2014/02/27 11:32:26]

It is enough for the test we are trying to fix.

 
     // Verify that all heaps are empty now.