Disables tooltips if we can't create the tooltip window. I still don't

views/widget/native_widget_win.h

 // 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.
 
 #ifndef VIEWS_WIDGET_NATIVE_WIDGET_WIN_H_
 #define VIEWS_WIDGET_NATIVE_WIDGET_WIN_H_
 #pragma once
 
 #include <atlbase.h>
 #include <atlapp.h>
@@ skipping 443 matching lines @@
   virtual void SetInitialFocus();
 
   // Executes the specified SC_command.
   void ExecuteSystemMenuCommand(int command);
 
   // Accessors and setters for various properties.
   void set_focus_on_creation(bool focus_on_creation) {
     focus_on_creation_ = focus_on_creation;
   }
 
-  // The TooltipManager.
+  // The TooltipManager. This is NULL if there is a problem creating the
+  // underlying tooltip window.
   // WARNING: RootView's destructor calls into the TooltipManager. As such, this
   // must be destroyed AFTER root_view_.
   scoped_ptr<TooltipManagerWin> tooltip_manager_;
 
   scoped_refptr<DropTargetWin> drop_target_;
 
   // Are a subclass of NativeWindowWin?
   bool is_window_;
 
   const gfx::Rect& invalid_rect() const { return invalid_rect_; }
@@ skipping 181 matching lines @@
   // Whether all ancestors have been enabled. This is only used if is_modal_ is
   // true.
   bool restored_enabled_;
 
   DISALLOW_COPY_AND_ASSIGN(NativeWidgetWin);
 };
 
 }  // namespace views
 
 #endif  // VIEWS_WIDGET_NATIVE_WIDGET_WIN_H_