Allow a Views client to provide a default frameview for window widgets.

ui/views/views_delegate.h

Index: ui/views/views_delegate.h
===================================================================
--- ui/views/views_delegate.h	(revision 117091)
+++ ui/views/views_delegate.h	(working copy)
@@ -27,6 +27,7 @@
 
 namespace views {
 
+class NonClientFrameView;
 class View;
 class Widget;
 
@@ -77,6 +78,12 @@
   virtual HICON GetDefaultWindowIcon() const = 0;
 #endif
 
+  // Creates a default NonClientFrameView to be used for windows that don't
+  // specify their own. If this function returns NULL, the
+  // views::CustomFrameView type will be used.
+  virtual NonClientFrameView* CreateDefaultNonClientFrameView(
+      Widget* widget) = 0;
+
   // AddRef/ReleaseRef are invoked while a menu is visible. They are used to
   // ensure we don't attempt to exit while a menu is showing.
   virtual void AddRef() = 0;