Factor out uses of the WebContentsModalDialog interface from platform-independent code

chrome/browser/ui/cocoa/constrained_web_dialog_delegate_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 "chrome/browser/ui/webui/constrained_web_dialog_delegate_base.h"
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/memory/scoped_nsobject.h"
 #import "chrome/browser/ui/cocoa/constrained_window/constrained_window_custom_sheet.h"
@@ skipping 28 matching lines @@
   }
   virtual WebDialogDelegate* GetWebDialogDelegate() OVERRIDE {
     return impl_->GetWebDialogDelegate();
   }
   virtual void OnDialogCloseFromWebUI() OVERRIDE {
     return impl_->OnDialogCloseFromWebUI();
   }
   virtual void ReleaseWebContentsOnDialogClose() OVERRIDE {
     return impl_->ReleaseWebContentsOnDialogClose();
   }
-  virtual WebContentsModalDialog* GetWindow() OVERRIDE {
-    return impl_->GetWindow();
+  virtual gfx::NativeWindow GetNativeWindow() OVERRIDE {
+    return impl_->GetNativeWindow();
   }
   virtual WebContents* GetWebContents() OVERRIDE {
     return impl_->GetWebContents();
   }
 
   // ConstrainedWindowMacDelegate interface
   virtual void OnConstrainedWindowClosed(
       ConstrainedWindowMac* window) OVERRIDE {
     if (!impl_->closed_via_webui())
       GetWebDialogDelegate()->OnDialogClosed("");
@@ skipping 24 matching lines @@
   window_.reset(
       [[ConstrainedWindowCustomWindow alloc] initWithContentRect:frame]);
   [GetWebContents()->GetNativeView() setFrame:frame];
   [[window_ contentView] addSubview:GetWebContents()->GetNativeView()];
 
   scoped_nsobject<CustomConstrainedWindowSheet> sheet(
       [[CustomConstrainedWindowSheet alloc]
           initWithCustomWindow:window_]);
   constrained_window_.reset(new ConstrainedWindowMac(
       this, web_contents, sheet));
-  return impl_->set_window(constrained_window_.get());
 }
 
 ConstrainedWebDialogDelegate* CreateConstrainedWebDialog(
         content::BrowserContext* browser_context,
         WebDialogDelegate* delegate,
         WebDialogWebContentsDelegate* tab_delegate,
         content::WebContents* web_contents) {
   // Deleted when the dialog closes.
   ConstrainedWebDialogDelegateMac* constrained_delegate =
       new ConstrainedWebDialogDelegateMac(
           browser_context, delegate, tab_delegate, web_contents);
   return constrained_delegate;
 }