[proxy] fixing harmony/proxy.js tests and improving error messages + some drive-by fixes

src/prototype.h

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_PROTOTYPE_H_
 #define V8_PROTOTYPE_H_
 
 #include "src/isolate.h"
 #include "src/objects.h"
 
@@ skipping 45 matching lines @@
         isolate_(receiver_map->GetIsolate()) {}
 
   explicit PrototypeIterator(Handle<Map> receiver_map)
       : did_jump_to_prototype_chain_(true),
         object_(NULL),
         handle_(handle(receiver_map->prototype(), receiver_map->GetIsolate())),
         isolate_(receiver_map->GetIsolate()) {}
 
   ~PrototypeIterator() {}
 
+  const bool HasAccess() {
+    Handle<JSObject> current;
+    if (handle_.is_null()) {
+      if (!object_->IsJSObject()) return true;
+      current = Handle<JSObject>(JSObject::cast(object_));
+    } else {
+      if (!handle_->IsJSObject()) return true;
+      current = Handle<JSObject>::cast(handle_);
+    }
+    if (current->IsJSGlobalProxy() || current->IsJSGlobalObject() ||
+        current->IsAccessCheckNeeded()) {
+      return isolate_->MayAccess(handle(isolate_->context()), current);
+    }
+    return true;
+  }
+
   template <typename T = Object>
   T* GetCurrent() const {
     DCHECK(handle_.is_null());
     return T::cast(object_);
   }
 
   template <typename T = Object>
   static Handle<T> GetCurrent(const PrototypeIterator& iterator) {
     DCHECK(!iterator.handle_.is_null());
     return Handle<T>::cast(iterator.handle_);
@@ skipping 76 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(PrototypeIterator);
 };
 
 
 }  // namespace internal
 
 }  // namespace v8
 
 #endif  // V8_PROTOTYPE_H_