Have panels respond to changes in work area on Linux.

chrome/browser/ui/panels/panel_browser_window_gtk.cc

Index: chrome/browser/ui/panels/panel_browser_window_gtk.cc
diff --git a/chrome/browser/ui/panels/panel_browser_window_gtk.cc b/chrome/browser/ui/panels/panel_browser_window_gtk.cc
index c9342e02c86ccdf031a714d97855f9a16d7598d2..11388c523785a8c0056449e4cc19b38dc2155643 100644
--- a/chrome/browser/ui/panels/panel_browser_window_gtk.cc
+++ b/chrome/browser/ui/panels/panel_browser_window_gtk.cc
@@ -70,6 +70,7 @@ PanelBrowserWindowGtk::~PanelBrowserWindowGtk() {
     DestroyDragWidget();
   }
   panel_->OnNativePanelClosed();
+  ui::WorkAreaWatcherX::RemoveObserver(this);
 }
 
 void PanelBrowserWindowGtk::Init() {
@@ -92,6 +93,8 @@ void PanelBrowserWindowGtk::Init() {
                    G_CALLBACK(OnTitlebarButtonPressEventThunk), this);
   g_signal_connect(titlebar_widget(), "button-release-event",
                    G_CALLBACK(OnTitlebarButtonReleaseEventThunk), this);
+
+  ui::WorkAreaWatcherX::AddObserver(this);
 }
 
 bool PanelBrowserWindowGtk::GetWindowEdge(int x, int y, GdkWindowEdge* edge) {
@@ -225,6 +228,10 @@ BrowserWindowGtk::TitleDecoration PanelBrowserWindowGtk::GetWindowTitle(
   }
 }
 
+void PanelBrowserWindowGtk::WorkAreaChanged() {
+  panel_->manager()->OnDisplayChanged();
+}
+
 void PanelBrowserWindowGtk::ShowPanel() {
   Show();
 }