Adds back some debugging code

ui/aura/window_observer.cc

+// Copyright (c) 2013 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 "ui/aura/window_observer.h"
+
+#include "base/debug/stack_trace.h"

[flackr, 2014/04/28 17:11:42]

This doesn't seem to be used.

[sky, 2014/04/28 17:18:36]

Done.

+#include "base/logging.h"
+#include "ui/aura/window.h"
+
+namespace aura {
+
+WindowObserver::WindowObserver() : observing_(0) {
+}
+
+WindowObserver::~WindowObserver() {
+  // TODO(flackr): Remove this check and observing_ counter when the cause of
+  // http://crbug.com/365364 is discovered.
+  CHECK_EQ(0, observing_);
+}
+
+void WindowObserver::OnObservingWindow(aura::Window* window) {
+  if (!window->HasObserver(this))
+    observing_++;
+}
+
+void WindowObserver::OnUnobservingWindow(aura::Window* window) {
+  if (window->HasObserver(this))
+    observing_--;
+}
+
+}  // namespace aura