Make instanceof and Object.getPrototypeOf work for proxies, plus a few other tweaks.

src/objects.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 620 matching lines @@
   if (IsSmi()) {
     Heap* heap = Isolate::Current()->heap();
     Context* context = heap->isolate()->context()->global_context();
     return context->number_function()->instance_prototype();
   }
 
   HeapObject* heap_object = HeapObject::cast(this);
 
   // The object is either a number, a string, a boolean,
   // a real JS object, or a Harmony proxy.
-  if (heap_object->IsJSObject() || heap_object->IsJSProxy()) {
+  if (heap_object->IsJSReceiver()) {
     return heap_object->map()->prototype();
   }
   Heap* heap = heap_object->GetHeap();
   Context* context = heap->isolate()->context()->global_context();
 
   if (heap_object->IsHeapNumber()) {
     return context->number_function()->instance_prototype();
   }
   if (heap_object->IsString()) {
     return context->string_function()->instance_prototype();
@@ skipping 2686 matching lines @@
     return JSObject::cast(proto)->LocalLookup(name, result);
   }
 
   // Do not use inline caching if the object is a non-global object
   // that requires access checks.
   if (!IsJSGlobalProxy() && IsAccessCheckNeeded()) {
     result->DisallowCaching();
   }
 
   // Check __proto__ before interceptor.
-  if (name->Equals(heap->Proto_symbol()) &&
-      !IsJSContextExtensionObject()) {
+  if (name->Equals(heap->Proto_symbol()) && !IsJSContextExtensionObject()) {
     result->ConstantResult(this);
     return;
   }
 
   // Check for lookup interceptor except when bootstrapping.
   if (HasNamedInterceptor() && !heap->isolate()->bootstrapper()->IsActive()) {
     result->InterceptorResult(this);
     return;
   }
 
@@ skipping 7350 matching lines @@
   if (break_point_objects()->IsUndefined()) return 0;
   // Single beak point.
   if (!break_point_objects()->IsFixedArray()) return 1;
   // Multiple break points.
   return FixedArray::cast(break_point_objects())->length();
 }
 #endif
 
 
 } }  // namespace v8::internal