Add tests to verify accelerators properly work on constrained window.

ui/views/test/test_widget_observer.cc

+// Copyright (c) 2012 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/views/test/test_widget_observer.h"
+
+#include "base/logging.h"
+#include "ui/views/widget/widget.h"
+
+namespace views {
+namespace test {
+
+TestWidgetObserver::TestWidgetObserver(Widget* widget)
+    : widget_(widget) {
+  widget_->AddObserver(this);
+}
+
+TestWidgetObserver::~TestWidgetObserver() {
+  if (widget_)
+    widget_->RemoveObserver(this);
+}
+
+void TestWidgetObserver::OnWidgetClosing(Widget* widget) {
+  DCHECK_EQ(widget_, widget);
+  widget_ = NULL;
+}
+
+}  // namespace test
+}  // namespace views