[proxies] fix access issue when having proxies on the prototype-chain of global objects.

src/prototype.h

Index: src/prototype.h
diff --git a/src/prototype.h b/src/prototype.h
index 2be43e4fbdc9d0794e8670938f709d77652d0387..f54192e0fc29289760f750daba139b709488c227 100644
--- a/src/prototype.h
+++ b/src/prototype.h
@@ -63,6 +63,17 @@ class PrototypeIterator {
 
   ~PrototypeIterator() {}
 
+  const bool HasAccess() {
+    // We can only perform access check in the handlified version of the
+    // PrototypeIterator.
+    DCHECK(!handle_.is_null());
+    if (handle_->IsAccessCheckNeeded()) {
+      return isolate_->MayAccess(handle(isolate_->context()),
+                                 Handle<JSObject>::cast(handle_));
+    }
+    return true;
+  }
+
   template <typename T = Object>
   T* GetCurrent() const {
     DCHECK(handle_.is_null());
@@ -72,6 +83,7 @@ class PrototypeIterator {
   template <typename T = Object>
   static Handle<T> GetCurrent(const PrototypeIterator& iterator) {
     DCHECK(!iterator.handle_.is_null());
+    DCHECK(iterator.object_ == NULL);
     return Handle<T>::cast(iterator.handle_);
   }