Splits TooltipManager so that it can be ported and stubs out the GTK...

views/widget/widget_gtk.h

Index: views/widget/widget_gtk.h
===================================================================
--- views/widget/widget_gtk.h	(revision 17063)
+++ views/widget/widget_gtk.h	(working copy)
@@ -16,6 +16,7 @@
 
 namespace views {
 
+class TooltipManagerGtk;
 class View;
 class WindowGtk;
 
@@ -172,6 +173,8 @@
   // The root of the View hierarchy attached to this window.
   scoped_ptr<RootView> root_view_;
 
+  scoped_ptr<TooltipManagerGtk> tooltip_manager_;
+
   // If true, the mouse is currently down.
   bool is_mouse_down_;