As discussed on the phone, I'd like your thoughts on the...

src/runtime.cc

Index: src/runtime.cc
===================================================================
--- src/runtime.cc	(revision 645)
+++ src/runtime.cc	(working copy)
@@ -5787,6 +5787,7 @@
   } else {
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
+    Counters::gc_last_resort_from_js.Increment();
     Heap::CollectAllGarbage();
   }
 }