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

chrome/browser/ui/cocoa/login_prompt_cocoa.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.
 
 #import "chrome/browser/ui/cocoa/login_prompt_cocoa.h"
 
 #include "base/mac/bundle_locations.h"
 #include "base/mac/mac_util.h"
 #include "base/memory/scoped_nsobject.h"
 #include "base/string16.h"
@@ skipping 59 matching lines @@
     // will occur via an InvokeLater on the UI thread, which is guaranteed
     // to happen after this is called (since this was InvokeLater'd first).
     WebContents* requesting_contents = GetWebContentsForLogin();
     DCHECK(requesting_contents);
 
     scoped_nsobject<CustomConstrainedWindowSheet> sheet(
         [[CustomConstrainedWindowSheet alloc]
             initWithCustomWindow:[sheet_controller_ window]]);
     constrained_window_.reset(new ConstrainedWindowMac(
         this, requesting_contents, sheet));
-    SetDialog(constrained_window_.get());
 
     NotifyAuthNeeded();
   }
 
+  virtual void CloseDialog() OVERRIDE {
+    // The hosting WebContentsModalDialog may have been freed.
+    if (constrained_window_.get())

[sail, 2013/02/16 21:45:22]

don't need .get()

[Mike Wittman, 2013/02/19 19:08:36]

Done.

+      constrained_window_->CloseWebContentsModalDialog();
+  }
+
   // Overridden from ConstrainedWindowMacDelegate:
   virtual void OnConstrainedWindowClosed(
       ConstrainedWindowMac* window) OVERRIDE {
     DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-    SetDialog(NULL);
     SetModel(NULL);
     ReleaseSoon();
 
     constrained_window_.reset();
     sheet_controller_.reset();
   }
 
   void OnLoginPressed(const string16& username,
                       const string16& password) {
     DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
@@ skipping 80 matching lines @@
   // Resize the text field.
   CGFloat windowDelta = [GTMUILocalizerAndLayoutTweaker
        sizeToFitFixedWidthTextField:explanationField_];
 
   NSRect newFrame = [[self window] frame];
   newFrame.size.height += windowDelta;
   [[self window] setFrame:newFrame display:NO];
 }
 
 @end