Bug 1275679 - Add option to the HTTP Networking preferences to disable Lightning user-agent addition. ui-r=Ratty r=IanN,Ratty a=IanN

suite/common/pref/pref-http.js

@@ -3,10 +3,13 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+var gLightningUAold;
+
 function Startup()
 {
   CheckPipelining();
   CheckPipeliningProxy();
+  CheckLightningUA();
 }
 
 function CheckPipelining()
@@ -24,3 +27,32 @@ function CheckPipeliningProxy()
   var enabled = prefHTTPVersion.value == "1.1";
   EnableElementById("enablePipeliningProxy", enabled, false);
 }
+
+// Lightning adds a UA token if calendar.useragent.extra is not empty.
+// Checkbox is visible if Lightning is installed and enabled.
+// Checkbox is checked if the pref contains any non-whitespace character.
+function CheckLightningUA()
+{
+  var prefLightningUA = document.getElementById("calendar.useragent.extra");
+  var boxLightningUA  = document.getElementById("uaLightningShow");
+
+  if (prefLightningUA.defaultValue)
+  {
+    boxLightningUA.hidden = false;
+    boxLightningUA.checked = prefLightningUA.value.trim() != "";
+    boxLightningUA.disabled = prefLightningUA.locked;
+    gLightningUAold = prefLightningUA.hasUserValue ? prefLightningUA.value : null;
+  }
+}
+
+// If the checkbox is checked, use previous user-set or default value.
+// If the checkbox is not checked, set the pref to an empty string.
+function OnLightningChanged(aChecked)
+{
+  var prefLightningUA = document.getElementById("calendar.useragent.extra");
+
+  if (aChecked && !gLightningUAold)
+    prefLightningUA.reset();
+  else
+    prefLightningUA.value = (aChecked && gLightningUAold) || "";
+}

suite/common/pref/pref-http.xul

@@ -27,6 +27,9 @@
       <preference id="general.useragent.compatMode.firefox"
                   name="general.useragent.compatMode.firefox"
                   type="bool"/>
+      <preference id="calendar.useragent.extra"
+                  name="calendar.useragent.extra"
+                  type="string"/>
     </preferences>
 
     <description>&prefPara;</description>
@@ -87,7 +90,14 @@
                 label="&prefFirefoxCompat.label;"
                 accesskey="&prefFirefoxCompat.accesskey;"
                 preference="general.useragent.compatMode.firefox"/>
+      <checkbox id="uaLightningShow"
+                hidden="true"
+                label="&prefLightningShow.label;"
+                accesskey="&prefLightningShow.accesskey;"
+                oncommand="OnLightningChanged(this.checked);"/>
     </groupbox>
+
+    <description>&prefCompatWarning;</description>
   </prefpane>
 
 </overlay>

suite/locales/en-US/chrome/common/help/cs_nav_prefs_advanced.xhtml

@@ -503,12 +503,19 @@
   <li><strong>User Agent String</strong>:
     The identifier sent by &brandShortName; to all websites is used for
     statistics about website usage but also sometimes to expose certain features
-    only to known browsers (a practice known as "sniffing").
+    only to known browsers (a practice known as "sniffing"). Consequently,
+    unchecking any of these boxes may result in websites or remote calendar
+    services not working properly.
     <ul>
       <li><strong>Advertise Firefox compatibility</strong>: If this is enabled,
         &brandShortName; will identify itself as both &brandShortName; and also
         compatible with Firefox. This allows websites that check for certain
         browsers rather than certain functionality to work with &brandShortName;.</li>
+      <li><strong>Advertise Lightning installation</strong>: This option is
+        only available when the Lightning calendar extension is installed and
+        activated. If this is enabled, &brandShortName; will add information on
+        Lightning being installed and which version, thus calendaring websites
+        and/or remote calendar services can customize their communication.</li>
     </ul>
   </li>
 </ul>

suite/locales/en-US/chrome/common/pref/pref-http.dtd

@@ -21,3 +21,6 @@
 <!ENTITY prefUseragent.label                 "User Agent String">
 <!ENTITY prefFirefoxCompat.label             "Advertise Firefox compatibility">
 <!ENTITY prefFirefoxCompat.accesskey         "F">
+<!ENTITY prefLightningShow.label             "Advertise Lightning installation">
+<!ENTITY prefLightningShow.accesskey         "L">
+<!ENTITY prefCompatWarning                   "WARNING: disabling these settings may result in websites or services not working properly.">