Mark maps having a hidden prototype rather than maps of hidden prototypes.

src/string-stream.cc

 // 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.
 
 #include "src/string-stream.h"
 
 #include "src/handles-inl.h"
 #include "src/prototype.h"
 
 namespace v8 {
@@ skipping 509 matching lines @@
     Add("%o", f);
     Add("/* warning: no JSFunction object or function name found */ ");
   }
 }
 
 
 void StringStream::PrintPrototype(JSFunction* fun, Object* receiver) {
   Object* name = fun->shared()->name();
   bool print_name = false;
   Isolate* isolate = fun->GetIsolate();
-  for (PrototypeIterator iter(isolate, receiver,
-                              PrototypeIterator::START_AT_RECEIVER);
-       !iter.IsAtEnd(); iter.Advance()) {
-    if (iter.GetCurrent()->IsJSObject()) {
+  if (receiver->IsNull() || receiver->IsUndefined() || receiver->IsJSProxy()) {
+    print_name = true;
+  } else {
+    if (!receiver->IsJSObject()) {
+      receiver = receiver->GetRootMap(isolate)->prototype();
+    }
+
+    for (PrototypeIterator iter(isolate, JSObject::cast(receiver),
+                                PrototypeIterator::START_AT_RECEIVER);
+         !iter.IsAtEnd(); iter.Advance()) {
       Object* key = iter.GetCurrent<JSObject>()->SlowReverseLookup(fun);
-      if (key != isolate->heap()->undefined_value()) {
+      if (!key->IsUndefined()) {
         if (!name->IsString() ||
             !key->IsString() ||
             !String::cast(name)->Equals(String::cast(key))) {
           print_name = true;
         }
         if (name->IsString() && String::cast(name)->length() == 0) {
           print_name = false;
         }
         name = key;
+        break;
       }
-    } else {
-      print_name = true;
     }
   }
   PrintName(name);
   // Also known as - if the name in the function doesn't match the name under
   // which it was looked up.
   if (print_name) {
     Add("(aka ");
     PrintName(fun->shared()->name());
     Put(')');
   }
@@ skipping 13 matching lines @@
   MemCopy(new_space, space_, *bytes);
   *bytes = new_bytes;
   DeleteArray(space_);
   space_ = new_space;
   return new_space;
 }
 
 
 }  // namespace internal
 }  // namespace v8