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

src/runtime/runtime-debug.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/runtime/runtime-utils.h"
 
 #include "src/arguments.h"
 #include "src/debug/debug.h"
 #include "src/debug/debug-evaluate.h"
 #include "src/debug/debug-frames.h"
@@ skipping 1291 matching lines @@
     instances->set(i, *wrapper);
   }
 
   // Return result as a JS array.
   Handle<JSObject> result =
       isolate->factory()->NewJSObject(isolate->array_function());
   JSArray::SetContent(Handle<JSArray>::cast(result), instances);
   return *result;
 }
 
-
-static bool HasInPrototypeChainIgnoringProxies(Isolate* isolate, Object* object,
+static bool HasInPrototypeChainIgnoringProxies(Isolate* isolate,
+                                               JSObject* object,
                                                Object* proto) {
   PrototypeIterator iter(isolate, object, PrototypeIterator::START_AT_RECEIVER);
   while (true) {
     iter.AdvanceIgnoringProxies();
     if (iter.IsAtEnd()) return false;
-    if (iter.IsAtEnd(proto)) return true;
+    if (iter.GetCurrent() == proto) return true;
   }
 }
 
 
 // Scan the heap for objects with direct references to an object
 // args[0]: the object to find references to
 // args[1]: constructor function for instances to exclude (Mirror)
 // args[2]: the the maximum number of objects to return
 RUNTIME_FUNCTION(Runtime_DebugReferencedBy) {
   HandleScope scope(isolate);
@@ skipping 86 matching lines @@
 // Find the effective prototype object as returned by __proto__.
 // args[0]: the object to find the prototype for.
 RUNTIME_FUNCTION(Runtime_DebugGetPrototype) {
   HandleScope shs(isolate);
   DCHECK(args.length() == 1);
   CONVERT_ARG_HANDLE_CHECKED(JSObject, obj, 0);
   Handle<Object> prototype;
   // TODO(1543): Come up with a solution for clients to handle potential errors
   // thrown by an intermediate proxy.
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, prototype,
-                                     Object::GetPrototype(isolate, obj));
+                                     JSReceiver::GetPrototype(isolate, obj));
   return *prototype;
 }
 
 
 // Patches script source (should be called upon BeforeCompile event).
 RUNTIME_FUNCTION(Runtime_DebugSetScriptSource) {
   HandleScope scope(isolate);
   DCHECK(args.length() == 2);
 
   CONVERT_ARG_HANDLE_CHECKED(JSValue, script_wrapper, 0);
@@ skipping 232 matching lines @@
   return Smi::FromInt(isolate->debug()->is_active());
 }
 
 
 RUNTIME_FUNCTION(Runtime_DebugBreakInOptimizedCode) {
   UNIMPLEMENTED();
   return NULL;
 }
 }  // namespace internal
 }  // namespace v8