WidgetDelegateView is its own contents view.

ash/mus/non_client_frame_controller.cc

Index: ash/mus/non_client_frame_controller.cc
diff --git a/ash/mus/non_client_frame_controller.cc b/ash/mus/non_client_frame_controller.cc
index 2c68b8fe1fa3ca742c411a76ace448ef683c89e7..b0a804582f939b90d8603faa7624d6967446815b 100644
--- a/ash/mus/non_client_frame_controller.cc
+++ b/ash/mus/non_client_frame_controller.cc
@@ -392,10 +392,6 @@ base::string16 NonClientFrameController::GetWindowTitle() const {
   return title;
 }
 
-views::View* NonClientFrameController::GetContentsView() {
-  return this;
-}
-
 bool NonClientFrameController::CanResize() const {
   return window_ &&
          (GetResizeBehavior(window_) & ui::mojom::kResizeBehaviorCanResize) !=