Have panels respond to changes in work area on Linux.

ui/base/x/work_area_watcher_x_observer.h

+// Copyright (c) 2011 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.
+
+#ifndef UI_BASE_X_WORK_AREA_WATCHER_X_OBSERVER_H_
+#define UI_BASE_X_WORK_AREA_WATCHER_X_OBSERVER_H_
+#pragma once
+
+#include "ui/base/ui_export.h"
+
+namespace ui {
+
+class UI_EXPORT WorkAreaWatcherXObserver {
+ public:
+  virtual void WorkAreaChanged() = 0;
+
+ protected:
+  virtual ~WorkAreaWatcherXObserver() {}
+};
+
+}  // namespace ui
+
+#endif  // UI_BASE_X_WORK_AREA_WATCHER_X_OBSERVER_H_