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

chrome/browser/media/router/media_routes_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_routes_observer.h"
-
-#include "base/logging.h"
-#include "chrome/browser/media/router/media_router.h"
-
-namespace media_router {
-
-MediaRoutesObserver::MediaRoutesObserver(MediaRouter* router)
-    : router_(router) {
-  DCHECK(router_);
-  if (!router_->RegisterMediaRoutesObserver(this))
-    LOG(ERROR) << "RegisterMediaRoutesObserver failed.";
-}
-
-MediaRoutesObserver::~MediaRoutesObserver() {
-  router_->UnregisterMediaRoutesObserver(this);
-}
-
-}  // namespace media_router