Issue #2652 - Part2: Add "Clear DNS cache" button to about:networking

Resolves #2652

toolkit/content/aboutNetworking.js

@@ -176,6 +176,14 @@ function init() {
     doLookup();
   });
 
+  let clearDNSCache = document.getElementById("clearDNSCache");
+  clearDNSCache.addEventListener("click", function() {
+    Cc["@mozilla.org/network/dns-service;1"]
+      .getService(Ci.nsIDNSService)
+      .clearCache();
+    requestAllNetworkingData();
+  });
+
   let setLogButton = document.getElementById("set-log-file-button");
   setLogButton.addEventListener("click", setLogFile);
 

toolkit/content/aboutNetworking.xhtml

@@ -96,6 +96,8 @@
           </div>
 
           <div id="dns" class="tab" hidden="true">
+              <button id="clearDNSCache">&aboutNetworking.clearDNSCache;</button>
+              <br/><br/>
               <table>
                   <thead>
                       <tr>

toolkit/locales/en-US/chrome/global/aboutNetworking.dtd

@@ -41,3 +41,4 @@
 <!ENTITY aboutNetworking.dnsLookupButton       "Resolve">
 <!ENTITY aboutNetworking.dnsDomain             "Domain">
 <!ENTITY aboutNetworking.dnsLookupTableColumn  "IPs">
+<!ENTITY aboutNetworking.clearDNSCache         "Clear DNS cache">