Have panels respond to changes in work area on Linux.

ui/base/x/root_window_property_watcher_x.h

Index: ui/base/x/root_window_property_watcher_x.h
diff --git a/ui/base/x/root_window_property_watcher_x.h b/ui/base/x/root_window_property_watcher_x.h
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+++ b/ui/base/x/root_window_property_watcher_x.h
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+// 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_ROOT_WINDOW_PROPERTY_WATCHER_X_H_
+#define UI_BASE_X_ROOT_WINDOW_PROPERTY_WATCHER_X_H_
+#pragma once
+
+#include <gdk/gdk.h>
+
+#include "base/memory/singleton.h"
+#include "ui/base/gtk/gtk_signal.h"
+#include "ui/base/ui_export.h"
+
+namespace ui {
+
+namespace internal {
+
+// This class keeps track of changes to properties on the root window. This is
+// not to be used directly. Implement a watcher for the specific property you're
+// interested in.
+class RootWindowPropertyWatcherX {
+ public:
+  static RootWindowPropertyWatcherX* GetInstance();
+
+ private:
+  friend struct DefaultSingletonTraits<RootWindowPropertyWatcherX>;
+
+  RootWindowPropertyWatcherX();
+  ~RootWindowPropertyWatcherX();
+
+  // Callback for PropertyChange XEvents.
+  CHROMEG_CALLBACK_1(RootWindowPropertyWatcherX, GdkFilterReturn,
+                     OnWindowXEvent, GdkXEvent*, GdkEvent*);
+
+  DISALLOW_COPY_AND_ASSIGN(RootWindowPropertyWatcherX);
+};
+
+}  // namespace internal
+
+}  // namespace ui
+
+#endif  // UI_BASE_X_ROOT_WINDOW_PROPERTY_WATCHER_X_H_