Have panels respond to changes in work area on Linux.

ui/base/x/work_area_watcher_x_observer.h

Index: ui/base/x/work_area_watcher_x_observer.h
diff --git a/ui/base/x/work_area_watcher_x_observer.h b/ui/base/x/work_area_watcher_x_observer.h
new file mode 100644
index 0000000000000000000000000000000000000000..b0c562b3fb3e5079ca52f77694b3fae69eb205d6
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+++ b/ui/base/x/work_area_watcher_x_observer.h
@@ -0,0 +1,23 @@
+// 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_