Switch the inheritance of WebView from WebWidget to protected.

content/renderer/render_widget.cc

 // 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.
 
 #include "content/renderer/render_widget.h"
 
 #include <memory>
 #include <utility>
 
 #include "base/auto_reset.h"
@@ skipping 1380 matching lines @@
 
   Send(new InputHostMsg_QueueSyntheticGesture(routing_id_, gesture_packet));
 }
 
 void RenderWidget::Close() {
   screen_metrics_emulator_.reset();
   WillCloseLayerTreeView();
   compositor_.reset();
   if (webwidget_) {
     webwidget_->close();
-    webwidget_ = NULL;
+    webwidget_ = nullptr;
   }
 }
 
 WebRect RenderWidget::windowRect() {
   if (pending_window_rect_count_)
     return pending_window_rect_;
 
   return view_screen_rect_;
 }
 
@@ skipping 662 matching lines @@
 }
 
 float RenderWidget::GetOriginalDeviceScaleFactor() const {
   return
       screen_metrics_emulator_ ?
       screen_metrics_emulator_->original_screen_info().deviceScaleFactor :
       device_scale_factor_;
 }
 
 }  // namespace content