Adding namespace-level comment for dns.idl. This will appear on the API summary page.

chrome/common/extensions/api/dns.idl

 // Copyright 2013 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.
 
+// Use the <code>chrome.dns</code> API for dns resolution.
 namespace dns {
 
   dictionary ResolveCallbackResolveInfo {
     // The result code. Zero indicates success.
     long resultCode;
 
     // A string representing the IP address literal. Supplied only if resultCode
     // indicates success. Note that we presently return only IPv4 addresses.
     DOMString? address;
   };
 
   callback ResolveCallback = void (ResolveCallbackResolveInfo resolveInfo);
 
   interface Functions {
     // Resolves the given hostname or IP address literal.
     // |hostname| : The hostname to resolve.
     // |callback| : Called when the resolution operation completes.
     static void resolve(DOMString hostname,
                         ResolveCallback callback);
   };
 
 };