Adding missing link to single purpose docs

chrome/common/extensions/docs/templates/articles/single_purpose.html

 <h1>Extensions Quality Guidelines FAQ</h1>
 
 <h2 id="one">1.) What is the new policy?</h2>
 
 <p>
 To maintain the quality of the Chrome user experience,
 we recently launched a new policy requiring Chrome extensions
 to have a single purpose.
 We are also introducing the new
 <a href="http://blog.chromium.org/2014/03/protecting-user-settings-on-windows.html">Settings Override API</a>
 to allow extensions to manage important Chrome settings on Windows.
 Beginning with the July 2014 release of Chrome,
 the Settings Override API will be the only approved path
 for offering settings changes to Chrome users on Windows.
 In addition, starting with the May 20, 2014 release of Chrome,
 we <a href="http://blog.chromium.org/2014/02/make-sure-to-get-your-extension-in.html">have begun to require</a>
 that extensions in Chrome for Windows be hosted in the Chrome Web Store.
 Starting in Chrome 44 in July 2015,
-extensions in Mac are also required to be hosted in the Chrome Web Store.
-</p>
+extensions in Mac are also
+<a href="http://blog.chromium.org/2015/05/continuing-to-protect-chrome-users-from.html">required to be hosted in the Chrome Web Store</a>.</p>
 
 <h2 id="two">2.) Why did Google launch a “single purpose” Chrome extensions policy?</h2>
 
 <p>For an overview of the policy announcement, please read this
 <a href="http://blog.chromium.org/2013/12/keeping-chrome-extensions-simple.html">Chromium blog post</a>.</p>
 
 <p>We launched this policy because
 multi-purpose extensions can crowd your browser UI
 and slow down your web browsing sometimes significantly.
 Speed and simplicity have always been part of Chrome's core principles,
@@ skipping 356 matching lines @@
 A search extension.
 It has multiple features, including this dropdown,
 but all of them are related to the narrow subject matter of search.
 </p>
 
 <img src="{{static}}/images/extension2.png"
      width="680"
      height="425"
      alt="Image of search extension">