Only (and always) put URLs in NSLinkAttributeName.

chrome/browser/ui/cocoa/one_click_signin_view_controller.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/one_click_signin_view_controller.h"
 
 #include "base/callback_helpers.h"
 #include "base/logging.h"
 #include "base/mac/bundle_locations.h"
 #import "chrome/browser/ui/chrome_style.h"
@@ skipping 238 matching lines @@
     messageText = learnMoreText;
   }
 
   NSColor* linkColor =
       gfx::SkColorToCalibratedNSColor(chrome_style::GetLinkColor());
   [informativeTextView_ setMessage:messageText
                           withFont:font
                       messageColor:[NSColor blackColor]];
   [informativeTextView_ addLinkRange:NSMakeRange(learnMoreOffset,
                                                  [learnMoreText length])
-                            withName:@""
+                             withURL:@(chrome::kChromeSyncLearnMoreURL)
                            linkColor:linkColor];
 
   // Make the "Advanced" link font as large as the "Learn More" link.
   [[advancedLink_ cell] setFont:font];
   [advancedLink_ sizeToFit];
 
   // Size to fit.
   [[informativePlaceholderTextField_ cell] setAttributedStringValue:
       [informativeTextView_ attributedString]];
   [GTMUILocalizerAndLayoutTweaker
@@ skipping 26 matching lines @@
                                 ui::PAGE_TRANSITION_LINK, false);
   webContents_->OpenURL(params);
   return YES;
 }
 
 - (void)close {
   base::ResetAndReturn(&closeCallback_).Run();
 }
 
 @end