Use GC-safe version when setting elements.

src/runtime.cc

Index: src/runtime.cc
diff --git a/src/runtime.cc b/src/runtime.cc
index e8e73552055f9ef2bed114803c2c371043aa7186..09115e0ee625c9bc1863563231660ce3a22c9ab5 100644
--- a/src/runtime.cc
+++ b/src/runtime.cc
@@ -7395,8 +7395,9 @@ static MaybeObject* Runtime_StoreContextSlot(Arguments args) {
       }
     } else {
       ASSERT((attributes & READ_ONLY) == 0);
-      Handle<JSObject>::cast(holder)->SetElement(index, *value)->
-          ToObjectUnchecked();
+      Handle<Object> result =
+          SetElement(Handle<JSObject>::cast(holder), index, value);
+      if (result.is_null()) return Failure::Exception();
     }
     return *value;
   }