diff -r 000000000000 -r 6474c204b198 toolkit/components/help/content/contextHelp.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/components/help/content/contextHelp.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,69 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# 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/.
+
+# Set the default content pack to the Mozilla content pack. Use the
+# setHelpFileURI function to set this value.
+var helpFileURI;
+
+# openHelp - Opens up the Mozilla Help Viewer with the specified
+#    topic and content pack.
+# see http://www.mozilla.org/projects/help-viewer/content_packs.html
+function openHelp(topic, contentPack)
+{
+# helpFileURI is the content pack to use in this function. If contentPack is defined,
+# use that and set the helpFileURI to that value so that it will be the default.
+  helpFileURI = contentPack || helpFileURI;
+
+# Try to find previously opened help.
+  var topWindow = locateHelpWindow(helpFileURI);
+
+  if ( topWindow ) {
+# Open topic in existing window.
+    topWindow.focus();
+    topWindow.displayTopic(topic);
+  } else {
+# Open topic in new window.
+    const params = Components.classes["@mozilla.org/embedcomp/dialogparam;1"]
+                             .createInstance(Components.interfaces.nsIDialogParamBlock);
+    params.SetNumberStrings(2);
+    params.SetString(0, helpFileURI);
+    params.SetString(1, topic);
+    const ww = Components.classes["@mozilla.org/embedcomp/window-watcher;1"]
+                         .getService(Components.interfaces.nsIWindowWatcher);
+#ifdef XP_WIN
+#define HELP_ALWAYS_RAISED_TOGGLE
+#endif
+#ifdef HELP_ALWAYS_RAISED_TOGGLE
+    ww.openWindow(null, "chrome://help/content/help.xul", "_blank", "chrome,all,alwaysRaised,dialog=no", params);
+#else
+    ww.openWindow(null, "chrome://help/content/help.xul", "_blank", "chrome,all,dialog=no", params);
+#endif
+  }
+}
+
+# setHelpFileURI - Sets the default content pack to use in the Help Viewer
+function setHelpFileURI(rdfURI)
+{
+  helpFileURI = rdfURI;
+}
+
+# Locate existing help window for this content pack.
+function locateHelpWindow(contentPack) {
+    const windowManagerInterface = Components
+        .classes['@mozilla.org/appshell/window-mediator;1'].getService()
+        .QueryInterface(Components.interfaces.nsIWindowMediator);
+    const iterator = windowManagerInterface.getEnumerator("mozilla:help");
+    var topWindow = null;
+    var aWindow;
+
+# Loop through help windows looking for one with selected content
+# pack.
+    while (iterator.hasMoreElements()) {
+        aWindow = iterator.getNext();
+        if (!aWindow.closed && aWindow.getHelpFileURI() == contentPack) {
+            topWindow = aWindow;
+        }
+    }
+    return topWindow;
+}