Move services code brought in from Mojo to live under //third_party.

mojo/services/view_manager/public/cpp/view_tracker.cc

-// Copyright 2014 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 "view_manager/public/cpp/view_tracker.h"
-
-namespace mojo {
-
-ViewTracker::ViewTracker() {
-}
-
-ViewTracker::~ViewTracker() {
-  for (Views::iterator i = views_.begin(); i != views_.end(); ++i)
-    (*i)->RemoveObserver(this);
-}
-
-void ViewTracker::Add(View* view) {
-  if (views_.count(view))
-    return;
-
-  view->AddObserver(this);
-  views_.insert(view);
-}
-
-void ViewTracker::Remove(View* view) {
-  if (views_.count(view)) {
-    views_.erase(view);
-    view->RemoveObserver(this);
-  }
-}
-
-bool ViewTracker::Contains(View* view) {
-  return views_.count(view) > 0;
-}
-
-void ViewTracker::OnViewDestroying(View* view) {
-  DCHECK_GT(views_.count(view), 0u);
-  Remove(view);
-}
-
-}  // namespace mojo