Fix inline constructors for Harmony Proxy prototypes.

src/runtime.cc

Index: src/runtime.cc
diff --git a/src/runtime.cc b/src/runtime.cc
index 93479d89a7daa1e009983eda722e73104a4decd0..be6e9353ded45b3a2718b156b1af1f87596fd0f9 100644
--- a/src/runtime.cc
+++ b/src/runtime.cc
@@ -10257,11 +10257,12 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_GetArrayKeys) {
 
 RUNTIME_FUNCTION(MaybeObject*, Runtime_LookupAccessor) {
   ASSERT(args.length() == 3);
-  CONVERT_ARG_CHECKED(JSObject, obj, 0);
+  CONVERT_ARG_CHECKED(JSReceiver, receiver, 0);
   CONVERT_ARG_CHECKED(String, name, 1);
   CONVERT_SMI_ARG_CHECKED(flag, 2);
   AccessorComponent component = flag == 0 ? ACCESSOR_GETTER : ACCESSOR_SETTER;
-  return obj->LookupAccessor(name, component);
+  if (!receiver->IsJSObject()) return isolate->heap()->undefined_value();
+  return JSObject::cast(receiver)->LookupAccessor(name, component);
 }