Cleans up gyp file for views example and removes duplicate code

ui/views/examples/tree_view_example.h

Index: ui/views/examples/tree_view_example.h
diff --git a/ui/views/examples/tree_view_example.h b/ui/views/examples/tree_view_example.h
index ffac4dd66fa4777771403f527465d29a055f432d..d70e791e4972f5cd2d1a2e25a4a34acc6da4a810 100644
--- a/ui/views/examples/tree_view_example.h
+++ b/ui/views/examples/tree_view_example.h
@@ -21,11 +21,12 @@ 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();