Move BroadcastChannel browser code from components/ to content/browser.

components/webmessaging/public/interfaces/broadcast_channel.mojom

-// Copyright 2016 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.
-
-module webmessaging.mojom;
-
-import "url/mojo/origin.mojom";
-
-// A pair of BroadcastChannelClient interfaces is used to represent a connection
-// to a particular channel. One client is implemented in the browser, for
-// messages sent from the renderer to the browser, and one client is implemented
-// in the renderer for messages from the browser to the renderer.
-interface BroadcastChannelClient {
-  // Messages are passed as SerializedScriptValue.
-  OnMessage(string message);
-};
-
-// This interface is used to set up connections to broadcast channels. All
-// connections to channels made from the same event loop should be made
-// through the same BroadcastChannelProvider connection to ensure correct
-// ordering of messages.
-// Typically the browser will have one instance of a BroadcastChannelProvider
-// per storage partition, to which all connections from renderers in that
-// partition are bound. This instance will then forward messages received on a
-// particular connection to all other connections in the same storage partition
-// with the same origin and name.
-interface BroadcastChannelProvider {
-  // Connect to the channel identified by the |origin| and |name|. Messages can
-  // be sent to the channel using |sender|, and messages to the channel will be
-  // received by |receiver|.
-  ConnectToChannel(url.mojom.Origin origin, string name,
-                   associated BroadcastChannelClient receiver,
-                   associated BroadcastChannelClient& sender);
-};