Cleans up gyp file for views example and removes duplicate code

ui/views/examples/tree_view_example.h

 // Copyright (c) 2012 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 UI_VIEWS_EXAMPLES_TREE_VIEW_EXAMPLE_H_
 #define UI_VIEWS_EXAMPLES_TREE_VIEW_EXAMPLE_H_
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "ui/base/models/simple_menu_model.h"
 #include "ui/base/models/tree_node_model.h"
 #include "ui/views/context_menu_controller.h"
 #include "ui/views/controls/button/button.h"
 #include "ui/views/controls/tree/tree_view_controller.h"
 #include "ui/views/examples/example_base.h"
 
 namespace views {
 
 class MenuRunner;
 class TreeView;
 
 namespace examples {
 
-class TreeViewExample : public ExampleBase,
-                        public ButtonListener,
-                        public TreeViewController,
-                        public ContextMenuController,
-                        public ui::SimpleMenuModel::Delegate {
+class VIEWS_EXAMPLES_EXPORT TreeViewExample
+    : public ExampleBase,
+      public ButtonListener,
+      public TreeViewController,
+      public ContextMenuController,
+      public ui::SimpleMenuModel::Delegate {
  public:
   TreeViewExample();
   virtual ~TreeViewExample();
 
   // ExampleBase:
   virtual void CreateExampleView(View* container) OVERRIDE;
 
  private:
   // IDs used by the context menu.
   enum MenuIDs {
@@ skipping 42 matching lines @@
 
   scoped_ptr<MenuRunner> context_menu_runner_;
 
   DISALLOW_COPY_AND_ASSIGN(TreeViewExample);
 };
 
 }  // namespace examples
 }  // namespace views
 
 #endif  // UI_VIEWS_EXAMPLES_TREE_VIEW_EXAMPLE_H_