Call ShowRootWindow on NativeWindow's RootWindow to display the window.

content/shell/shell.h

Index: content/shell/shell.h
diff --git a/content/shell/shell.h b/content/shell/shell.h
index 3c9e6ba9260b97ca9d8799b21db9ee6a05ff3487..f3426132eb46d604287614a9b1e434719e0069c5 100644
--- a/content/shell/shell.h
+++ b/content/shell/shell.h
@@ -63,7 +63,7 @@ class Shell : public WebContentsDelegate,
   void CloseDevTools();
 
   // Do one time initialization at application startup.
-  static void PlatformInitialize();
+  static void Initialize();
 
   static Shell* CreateNewWindow(BrowserContext* browser_context,
                                 const GURL& url,
@@ -147,6 +147,9 @@ class Shell : public WebContentsDelegate,
   // Helper to create a new Shell given a newly created WebContents.
   static Shell* CreateShell(WebContents* web_contents);
 
+  // Helper for one time initialization of application
+  static void PlatformInitialize(const gfx::Size& default_window_size);
+
   // All the methods that begin with Platform need to be implemented by the
   // platform specific Shell implementation.
   // Called from the destructor to let each platform do any necessary cleanup.