[Aura] Support always-on-top top level window.

ui/base/x/x11_util.h

Index: ui/base/x/x11_util.h
diff --git a/ui/base/x/x11_util.h b/ui/base/x/x11_util.h
index f9e979c4ba86febed77e58ec03511e9daeaac131..888e76ae6d9b8e704e2ed80be4ed1ad758e58614 100644
--- a/ui/base/x/x11_util.h
+++ b/ui/base/x/x11_util.h
@@ -68,6 +68,10 @@ UI_EXPORT bool QueryRenderSupport(Display* dpy);
 // Return the default screen number for the display
 int GetDefaultScreen(Display* display);
 
+// TODO(xiyuan): Fix the stale XCursorCache problem per http://crbug.com/102759.
+// A special cursor that makes GetXCursor below to clear its XCursorCache.
+const int kCursorClearXCursorCache = -1;
+
 // Returns an X11 Cursor, sharable across the process.
 // |cursor_shape| is an X font cursor shape, see XCreateFontCursor().
 UI_EXPORT Cursor GetXCursor(int cursor_shape);