Attempt to fix GC mole failures.

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index 2a86e1bef11dcd72c48c928e35be046e1d559f80..f76a0cf40aeea1103af3675ad82656b64fdaeb05 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -2830,10 +2830,14 @@ void Heap::CreateInitialObjects() {
   set_instanceof_cache_map(Smi::FromInt(0));
   set_instanceof_cache_answer(Smi::FromInt(0));
 
-#define SYMBOL_INIT(name) \
-  roots_[k##name##RootIndex] = *factory->NewPrivateOwnSymbol();
-  PRIVATE_SYMBOL_LIST(SYMBOL_INIT)
+  {
+    HandleScope scope(isolate());
+#define SYMBOL_INIT(name)                               \
+  Handle<Symbol> name = factory->NewPrivateOwnSymbol(); \
+  roots_[k##name##RootIndex] = *name;
+    PRIVATE_SYMBOL_LIST(SYMBOL_INIT)
 #undef SYMBOL_INIT
+  }
 
   CreateFixedStubs();