Fix Array.prototype.sort on proxies.

src/runtime/runtime-array.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/conversions-inl.h"
 #include "src/elements.h"
 #include "src/factory.h"
@@ skipping 102 matching lines @@
 
 // Moves all own elements of an object, that are below a limit, to positions
 // starting at zero. All undefined values are placed after non-undefined values,
 // and are followed by non-existing element. Does not change the length
 // property.
 // Returns the number of non-undefined elements collected.
 // Returns -1 if hole removal is not supported by this method.
 RUNTIME_FUNCTION(Runtime_RemoveArrayHoles) {
   HandleScope scope(isolate);
   DCHECK(args.length() == 2);
-  CONVERT_ARG_HANDLE_CHECKED(JSObject, object, 0);
+  CONVERT_ARG_HANDLE_CHECKED(JSReceiver, object, 0);
   CONVERT_NUMBER_CHECKED(uint32_t, limit, Uint32, args[1]);
-  return *JSObject::PrepareElementsForSort(object, limit);
+  if (object->IsJSProxy()) return Smi::FromInt(-1);
+  return *JSObject::PrepareElementsForSort(Handle<JSObject>::cast(object),
+                                           limit);
 }
 
 
 // Move contents of argument 0 (an array) to argument 1 (an array)
 RUNTIME_FUNCTION(Runtime_MoveArrayContents) {
   HandleScope scope(isolate);
   DCHECK(args.length() == 2);
   CONVERT_ARG_HANDLE_CHECKED(JSArray, from, 0);
   CONVERT_ARG_HANDLE_CHECKED(JSArray, to, 1);
   JSObject::ValidateElements(from);
@@ skipping 359 matching lines @@
   CONVERT_ARG_HANDLE_CHECKED(Object, original_array, 0);
   Handle<Object> constructor;
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
       isolate, constructor,
       Object::ArraySpeciesConstructor(isolate, original_array));
   return *constructor;
 }
 
 }  // namespace internal
 }  // namespace v8