PlzNavigate: fix timing issue in app window creation

extensions/browser/app_window/app_window_contents.h

 // Copyright 2013 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.
 
 #ifndef EXTENSIONS_BROWSER_APP_WINDOW_APP_WINDOW_CONTENTS_H_
 #define EXTENSIONS_BROWSER_APP_WINDOW_APP_WINDOW_CONTENTS_H_
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "content/public/browser/web_contents_observer.h"
@@ skipping 24 matching lines @@
   void NativeWindowChanged(NativeAppWindow* native_app_window) override;
   void NativeWindowClosed() override;
   void DispatchWindowShownForTests() const override;
   void OnWindowReady() override;
   content::WebContents* GetWebContents() const override;
   WindowController* GetWindowController() const override;
 
  private:
   // content::WebContentsObserver
   bool OnMessageReceived(const IPC::Message& message) override;
+  void ReadyToCommitNavigation(content::NavigationHandle* handle) override;
 
   void UpdateDraggableRegions(const std::vector<DraggableRegion>& regions);
   void SuspendRenderFrameHost(content::RenderFrameHost* rfh);
 
   AppWindow* host_;  // This class is owned by |host_|
   GURL url_;
   scoped_ptr<content::WebContents> web_contents_;
   bool is_blocking_requests_;
   bool is_window_ready_;
 
   DISALLOW_COPY_AND_ASSIGN(AppWindowContentsImpl);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_BROWSER_APP_WINDOW_APP_WINDOW_CONTENTS_H_