Bug 1562084 - Description for non proxy-ing localhost r=fluent-reviewers,Gijs,flod

Differential Revision: https://phabricator.services.mozilla.com/D36277

--HG--
extra : moz-landing-system : lando

browser/components/preferences/connection.js

@@ -162,6 +162,9 @@ var gConnectionsDialog = {
     autoconfigURLPref.disabled = proxyTypePref.value != 2 || autoconfigURLPref.locked;
 
     this.updateReloadButton();
+
+    document.getElementById("networkProxyNoneLocalhost").hidden =
+        Services.prefs.getBoolPref("network.proxy.allow_hijacking_localhost", false);
   },
 
   updateDNSPref() {

browser/components/preferences/connection.xul

@@ -142,6 +142,8 @@
   <label data-l10n-id="connection-proxy-noproxy" control="networkProxyNone"/>
   <html:textarea id="networkProxyNone" preference="network.proxy.no_proxies_on" rows="2"/>
   <label control="networkProxyNone" data-l10n-id="connection-proxy-noproxy-desc" />
+  <label id="networkProxyNoneLocalhost" control="networkProxyNone" data-l10n-id="connection-proxy-noproxy-localhost-desc" />
+  <separator class="thin"/>
   <checkbox id="autologinProxy"
             data-l10n-id="connection-proxy-autologin"
             preference="signon.autologin.proxy" />

browser/locales/en-US/browser/preferences/connection.ftl

@@ -65,6 +65,9 @@ connection-proxy-noproxy = No proxy for
 
 connection-proxy-noproxy-desc = Example: .mozilla.org, .net.nz, 192.168.1.0/24
 
+# Do not translate localhost, 127.0.0.1 and ::1.
+connection-proxy-noproxy-localhost-desc = Connections to localhost, 127.0.0.1, and ::1 are never proxied.
+
 connection-proxy-autotype =
     .label = Automatic proxy configuration URL
     .accesskey = A