Revert of [Media Router] Design MediaRouter interface with stub implementation.

chrome/browser/media/router/media_sinks_observer.cc

-// 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.
-
-#include "chrome/browser/media/router/media_sinks_observer.h"
-
-#include "base/logging.h"
-#include "chrome/browser/media/router/media_router.h"
-
-namespace media_router {
-
-MediaSinksObserver::MediaSinksObserver(MediaRouter* router,
-                                       const MediaSource& source)
-    : source_(source), router_(router) {
-  DCHECK(router_);
-  if (!router_->RegisterMediaSinksObserver(this))
-    LOG(ERROR) << "RegisterMediaSinksObserver failed: " << source.ToString();
-}
-
-MediaSinksObserver::~MediaSinksObserver() {
-  router_->UnregisterMediaSinksObserver(this);
-}
-
-}  // namespace media_router