views: Add support for absolute positioned overlay views.

To test:
Run `cefclient.exe --use-views --hide-frame --hide-controls`
Add `--enable-chrome-runtime` for the same behavior using the Chrome location
bar instead of a text field.

include/views/cef_view_delegate.h

@@ -108,9 +108,16 @@ class CefViewDelegate : public virtual CefBaseRefCounted {
   ///
   // Called when |view| is added or removed from the CefWindow.
   ///
-  /*--cef(optional_param=window)--*/
+  /*--cef()--*/
   virtual void OnWindowChanged(CefRefPtr<CefView> view, bool added) {}
 
+  ///
+  // Called when the layout of |view| has changed.
+  ///
+  /*--cef()--*/
+  virtual void OnLayoutChanged(CefRefPtr<CefView> view,
+                               const CefRect& new_bounds) {}
+
   ///
   // Called when |view| gains focus.
   ///