Keep the mouse cursor within desktop

ash/shell.h

Index: ash/shell.h
diff --git a/ash/shell.h b/ash/shell.h
index 23a13cdce010f8f3f05b1c2a265379da7f578859..f828919ba06faae67404fe65b17b6a595057f6ca 100644
--- a/ash/shell.h
+++ b/ash/shell.h
@@ -63,6 +63,7 @@ class DragDropController;
 class FocusCycler;
 class InputMethodEventFilter;
 class MonitorController;
+class MonitorChangeObserverX11;
 class PartialScreenshotEventFilter;
 class ResizeShadowController;
 class RootWindowEventFilter;
@@ -248,6 +249,10 @@ class ASH_EXPORT Shell {
   // when the screen is initially created.
   static bool initially_hide_cursor_;
 
+#if defined(USE_X11)
+  scoped_ptr<internal::MonitorChangeObserverX11> monitor_change_observer_;
+#endif
+
   scoped_ptr<aura::RootWindow> root_window_;
   ScreenAsh* screen_;