Have panels respond to changes in work area on Linux.

ui/base/x/work_area_watcher_x.cc

+// 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.
+
+#include "ui/base/x/work_area_watcher_x.h"
+
+#include "ui/base/x/root_window_property_watcher_x.h"
+#include "ui/base/x/x11_util.h"
+
+namespace ui {
+
+static const char* kNetWorkArea = "_NET_WORKAREA";
+
+// static
+WorkAreaWatcherX* WorkAreaWatcherX::GetInstance() {
+  return Singleton<WorkAreaWatcherX>::get();
+}
+
+// static
+void WorkAreaWatcherX::AddObserver(Observer* observer) {
+  // Ensure that RootWindowPropertyWatcherX exists.
+  RootWindowPropertyWatcherX::GetInstance();
+  GetInstance()->observers_.AddObserver(observer);
+}
+
+// static
+void WorkAreaWatcherX::RemoveObserver(Observer* observer) {
+  GetInstance()->observers_.RemoveObserver(observer);
+}
+
+// static
+void WorkAreaWatcherX::Notify() {
+  GetInstance()->NotifyWorkAreaChanged();
+}
+
+// static
+Atom WorkAreaWatcherX::GetPropertyAtom() {
+  return GetAtomForScreenProperty(kNetWorkArea);
+}
+
+void WorkAreaWatcherX::NotifyWorkAreaChanged() {
+  FOR_EACH_OBSERVER(Observer, observers_, WorkAreaChanged());
+}
+
+}  // namespace ui