Fix JSON parser Handle leak

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index 5af21e18c0df762e7efb97e2778e6e708ad8f066..6d78b03a96e3379981ad6f57246dfafa3b8cd790 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -618,6 +618,7 @@ void Heap::GarbageCollectionEpilogue() {
   if (FLAG_gc_verbose) Print();
   if (FLAG_code_stats) ReportCodeStatistics("After GC");
 #endif
+  if (FLAG_check_handle_count) CheckHandleCount();
   if (FLAG_deopt_every_n_garbage_collections > 0) {
     // TODO(jkummerow/ulan/jarin): This is not safe! We can't assume that
     // the topmost optimized frame can be deoptimized safely, because it
@@ -5649,6 +5650,24 @@ void Heap::PrintHandles() {
 
 #endif
 
+class CheckHandleCountVisitor : public ObjectVisitor {
+ public:
+  CheckHandleCountVisitor() : handle_count_(0) {}
+  ~CheckHandleCountVisitor() { CHECK(handle_count_ < 1000); }
+  void VisitPointers(Object** start, Object** end) {
+    handle_count_ += end - start;
+  }
+
+ private:
+  ptrdiff_t handle_count_;
+};
+
+
+void Heap::CheckHandleCount() {
+  CheckHandleCountVisitor v;
+  isolate_->handle_scope_implementer()->Iterate(&v);
+}
+
 
 Space* AllSpaces::next() {
   switch (counter_++) {