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

chrome/browser/ui/login/login_prompt.h

Index: chrome/browser/ui/login/login_prompt.h
diff --git a/chrome/browser/ui/login/login_prompt.h b/chrome/browser/ui/login/login_prompt.h
index 21978111210d5d8bdc82ed89c27fe171cf82d68a..751781feb0a8be7e0ba716a39374af7fd79806ee 100644
--- a/chrome/browser/ui/login/login_prompt.h
+++ b/chrome/browser/ui/login/login_prompt.h
@@ -13,7 +13,6 @@
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/resource_dispatcher_host_login_delegate.h"
 
-class WebContentsModalDialog;
 class GURL;
 
 namespace content {
@@ -83,14 +82,15 @@ class LoginHandler : public content::ResourceDispatcherHostLoginDelegate,
 
   void SetModel(LoginModel* model);
 
-  void SetDialog(WebContentsModalDialog* dialog);
-
   // Notify observers that authentication is needed.
   void NotifyAuthNeeded();
 
   // Performs necessary cleanup before deletion.
   void ReleaseSoon();
 
+  // Closes the native dialog.
+  virtual void CloseDialog() = 0;
+
  private:
   // Starts observing notifications from other LoginHandlers.
   void AddObservers();
@@ -123,10 +123,6 @@ class LoginHandler : public content::ResourceDispatcherHostLoginDelegate,
   bool handled_auth_;
   mutable base::Lock handled_auth_lock_;
 
-  // The WebContentsModalDialog that is hosting our LoginView.
-  // This should only be accessed on the UI loop.
-  WebContentsModalDialog* dialog_;
-
   // Who/where/what asked for the authentication.
   scoped_refptr<net::AuthChallengeInfo> auth_info_;