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

content/shell/shell_mac.mm

 // 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/shell/shell.h"
 
 #include <algorithm>
 
 #include "base/logging.h"
 #import "base/memory/scoped_nsobject.h"
@@ skipping 119 matching lines @@
   [button setKeyEquivalent:key];
   [button setKeyEquivalentModifierMask:modifier];
   [parent addSubview:button];
   rect->origin.x += kButtonWidth;
 }
 
 }  // namespace
 
 namespace content {
 
-void Shell::PlatformInitialize() {
+void Shell::PlatformInitialize(const gfx::Size& default_window_size) {
 }
 
 void Shell::PlatformCleanUp() {
 }
 
 void Shell::PlatformEnableUIControl(UIControl control, bool is_enabled) {
   int id;
   switch (control) {
     case BACK_BUTTON:
       id = IDC_NAV_BACK;
@@ skipping 153 matching lines @@
         [[event.os_event characters] isEqual:@"l"]) {
       [window_ makeFirstResponder:url_edit_view_];
       return;
     }
 
     [[NSApp mainMenu] performKeyEquivalent:event.os_event];
   }
 }
 
 }  // namespace content