Implement author-constructible ReadableStream using V8 extras

third_party/WebKit/Source/core/streams/ReadableStreamTempStub.js

Index: third_party/WebKit/Source/core/streams/ReadableStreamTempStub.js
diff --git a/third_party/WebKit/Source/core/streams/ReadableStreamTempStub.js b/third_party/WebKit/Source/core/streams/ReadableStreamTempStub.js
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+++ b/third_party/WebKit/Source/core/streams/ReadableStreamTempStub.js
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+// Copyright 2015 The Chromium 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(global, binding, v8) {
+  'use strict';
+
+  // This file exists to help in the transition between IDL-implemented ReadableStream and V8 extras-implemented
+  // ReadableStream. Before it was introduced, there was an IDL-implemented property of the global object named
+  // "ReadableStream" that had no useful behavior, but might have been depended on by web code for some reason.
+
+  // This file thus emulates that old IDL-implemented property, _when experimental web platform features are disabled_.
+  // When experimental web platform features are _enabled_, the definition of global.ReadableStream in
+  // ReadableStream.js takes priority.
+
+  // Eventually, when the ReadableStream.js implementation is ready to be enabled by default, we can remove this file.
+
+  const TypeError = global.TypeError;
+  const defineProperty = global.Object.defineProperty;
+
+  class ReadableStream {
+    constructor() {
+      throw new TypeError('Illegal constructor');
+    }
+
+    getReader() {
+      throw new TypeError('Illegal invocation');
+    }
+
+    cancel() {
+      throw new TypeError('Illegal invocation');
+    }
+  }
+
+  defineProperty(global, 'ReadableStream', {
+    value: ReadableStream,
+    enumerable: false,
+    configurable: true,
+    writable: true
+  });
+});