Restore per-TypedArray-class length accessors as a perf workaround

test/mjsunit/es6/typedarray-proto.js

 // Copyright 2015 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.
 
 // Test that the methods for different TypedArray types have the same
 // identity.
 
 'use strict';
 
 let typedArrayConstructors = [
@@ skipping 10 matching lines @@
 let TypedArray = Uint8Array.__proto__;
 let TypedArrayPrototype = TypedArray.prototype;
 
 assertEquals(TypedArray.__proto__, Function.prototype);
 assertEquals(TypedArrayPrototype.__proto__, Object.prototype);
 
 // There are extra own class properties due to it simply being a function
 let classProperties = new Set([
   "length", "name", "arguments", "caller", "prototype", "BYTES_PER_ELEMENT"
 ]);
-let instanceProperties = new Set(["BYTES_PER_ELEMENT", "constructor", "prototype"]);
+let instanceProperties = new Set([
+  "BYTES_PER_ELEMENT", "constructor", "prototype",
+  // length is also an instance property as a temporary workaround to
+  // BUG(chromium:579905). TODO(littledan): remove the workaround
+  "length"
+]);
 
 function functionProperties(object) {
   return Object.getOwnPropertyNames(object).filter(function(name) {
     return typeof Object.getOwnPropertyDescriptor(object, name).value
-        == "function"
-      && name != 'constructor' && name != 'subarray';
+        == "function" && name != 'constructor';
   });
 }
 
 let typedArrayMethods = functionProperties(Uint8Array.prototype);
 let typedArrayClassMethods = functionProperties(Uint8Array);
 
 for (let constructor of typedArrayConstructors) {
   for (let property of Object.getOwnPropertyNames(constructor.prototype)) {
     assertTrue(instanceProperties.has(property), property);
   }
@@ skipping 13 matching lines @@
 assertFalse(desc.writable);
 assertFalse(desc.configurable);
 assertFalse(desc.enumerable);
 
 for (let constructor of typedArrayConstructors) {
   let desc = Object.getOwnPropertyDescriptor(constructor, "prototype");
   assertFalse(desc.writable);
   assertFalse(desc.configurable);
   assertFalse(desc.enumerable);
 }