diff -r 000000000000 -r 6474c204b198 browser/metro/base/content/contenthandlers/PluginHelper.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/metro/base/content/contenthandlers/PluginHelper.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,95 @@
+/* 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/. */
+"use strict";
+
+dump("### PluginHelper.js loaded\n");
+
+/**
+ * Handle events generated by plugin click-to-play code.
+ *
+ * This "PluginBindingAttached" fires when a "pluginProblem" XBL binding is
+ * created.  This binding overlays plugin content when the plugin is missing,
+ * blocked, click-to-play, or replaced by a "preview" extension plugin like
+ * Shumway or PDF.js.
+ */
+var PluginHelper = {
+  init: function () {
+    addEventListener("PluginBindingAttached", this, true, true);
+  },
+
+  handleEvent: function handleEvent(aEvent) {
+    switch (aEvent.type) {
+      case "PluginBindingAttached":
+        this.handlePluginBindingAttached(aEvent);
+        break;
+    }
+  },
+
+  getPluginMimeType: function (plugin) {
+    var tagMimetype = plugin.actualType;
+
+    if (tagMimetype == "") {
+      tagMimetype = plugin.type;
+    }
+    return tagMimetype;
+  },
+
+  handlePluginBindingAttached: function (aEvent) {
+    let plugin = aEvent.target;
+    let doc = plugin.ownerDocument;
+    let overlay = doc.getAnonymousElementByAttribute(plugin, "anonid", "main");
+    if (!overlay || overlay._bindingHandled) {
+      return;
+    }
+    overlay._bindingHandled = true;
+
+    let eventType = PluginHelper._getBindingType(plugin);
+    if (!eventType) {
+      return;
+    }
+
+    switch  (eventType) {
+      case "PluginPlayPreview": {
+        // Load the "preview" handler (an extension plugin like Shumway or PDF.js).
+        let previewContent = doc.getAnonymousElementByAttribute(plugin, "class", "previewPluginContent");
+        let pluginHost = Cc["@mozilla.org/plugin/host;1"].getService(Ci.nsIPluginHost);
+        let mimeType = PluginHelper.getPluginMimeType(plugin);
+        let playPreviewInfo = pluginHost.getPlayPreviewInfo(mimeType);
+
+        let iframe = previewContent.getElementsByClassName("previewPluginContentFrame")[0];
+        if (!iframe) {
+          // lazy initialization of the iframe
+          iframe = doc.createElementNS("http://www.w3.org/1999/xhtml", "iframe");
+          iframe.className = "previewPluginContentFrame";
+          previewContent.appendChild(iframe);
+        }
+        iframe.src = playPreviewInfo.redirectURL;
+        break;
+      }
+
+      case "PluginNotFound": {
+        // TODO: Display a message about missing plugins (bug 936907)
+        break;
+      }
+    }
+  },
+
+  // Helper to get the binding handler type from a plugin object
+  _getBindingType: function(plugin) {
+    if (!(plugin instanceof Ci.nsIObjectLoadingContent))
+      return null;
+
+    switch (plugin.pluginFallbackType) {
+      case Ci.nsIObjectLoadingContent.PLUGIN_UNSUPPORTED:
+        return "PluginNotFound";
+      case Ci.nsIObjectLoadingContent.PLUGIN_PLAY_PREVIEW:
+        return "PluginPlayPreview";
+      default:
+        // Metro Firefox does not yet support other fallback types.
+        return null;
+    }
+  },
+};
+
+PluginHelper.init();