[builtins] Fix missing check in Array.prototype.filter.

This fixes a missing fast-path check in the code-stub implementation of
the {Array.prototype.filter} method. Appending to the target JSArray is
only correct if the underlying length did not change.

R=jgruber@chromium.org
TEST=mjsunit/regress/regress-6657
BUG=v8:6657

Change-Id: Ida8d3511485b649b70d9a4b161742d494ebe4dac
Reviewed-on: https://chromium-review.googlesource.com/600467Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47156}

src/builtins/builtins-array-gen.cc

@@ -116,6 +116,7 @@ class ArrayBuiltinCodeStubAssembler : public CodeStubAssembler {
 
       BIND(&fast);
       {
+        GotoIf(SmiNotEqual(LoadJSArrayLength(a()), to_.value()), &runtime);
         kind = EnsureArrayPushable(a(), &runtime);
         GotoIf(IsElementsKindGreaterThan(kind, HOLEY_SMI_ELEMENTS),
                &object_push_pre);

test/mjsunit/regress/regress-6657.js

+// Copyright 2017 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.
+
+(function TestArrayNonEmptySpecies() {
+  class MyArray extends Array {
+    constructor() { return [1, 2, 3]; }
+  }
+  var a = [5, 4];
+  a.__proto__ = MyArray.prototype;
+  var o = a.filter(() => true);
+  assertEquals([5, 4, 3], o);
+  assertEquals(3, o.length);
+})();
+
+(function TestArrayLeakingSpeciesInsertInCallback() {
+  var my_array = [];
+  class MyArray extends Array {
+    constructor() { return my_array; }
+  }
+  var a = [5, 4];
+  a.__proto__ = MyArray.prototype;
+  var o = a.filter(() => (my_array[2] = 3, true));
+  assertEquals([5, 4, 3], o);
+  assertEquals(3, o.length);
+})();
+
+(function TestArrayLeakingSpeciesRemoveInCallback() {
+  var my_array = [];
+  class MyArray extends Array {
+    constructor() { return my_array; }
+  }
+  var a = [5, 4, 3, 2, 1];
+  a.__proto__ = MyArray.prototype;
+  var o = a.filter(() => (my_array.length = 0, true));
+  assertEquals([,,,,1], o);
+  assertEquals(5, o.length);
+})();