--- a/browser/components/customizableui/CustomizableUI.jsm
+++ b/browser/components/customizableui/CustomizableUI.jsm
@@ -1441,16 +1441,19 @@ var CustomizableUIInternal = {
       // By using this as the default, if a widget provides a full string rather
       // than a string ID for localization, we will fall back to that string
       // and return that.
       def = aDef || name;
     } else {
       name = aWidget.id + "." + aProp;
       def = aDef || "";
     }
+    if (aWidget.localized === false) {
+      return def;
+    }
     try {
       if (Array.isArray(aFormatArgs) && aFormatArgs.length) {
         return gWidgetsBundle.formatStringFromName(name, aFormatArgs,
           aFormatArgs.length) || def;
       }
       return gWidgetsBundle.GetStringFromName(name) || def;
     } catch (ex) {
       // If an empty string was explicitly passed, treat it as an actual
@@ -2313,16 +2316,17 @@ var CustomizableUIInternal = {
 
   // XXXunf Log some warnings here, when the data provided isn't up to scratch.
   normalizeWidget(aData, aSource) {
     let widget = {
       implementation: aData,
       source: aSource || CustomizableUI.SOURCE_EXTERNAL,
       instances: new Map(),
       currentArea: null,
+      localized: true,
       removable: true,
       overflows: true,
       defaultArea: null,
       shortcutId: null,
       tabSpecific: false,
       tooltiptext: null,
       showInPrivateBrowsing: true,
       _introducedInVersion: -1,
@@ -2348,17 +2352,18 @@ var CustomizableUIInternal = {
 
     const kOptStringProps = ["label", "tooltiptext", "shortcutId"];
     for (let prop of kOptStringProps) {
       if (typeof aData[prop] == "string") {
         widget[prop] = aData[prop];
       }
     }
 
-    const kOptBoolProps = ["removable", "showInPrivateBrowsing", "overflows", "tabSpecific"];
+    const kOptBoolProps = ["removable", "showInPrivateBrowsing", "overflows", "tabSpecific",
+                           "localized"];
     for (let prop of kOptBoolProps) {
       if (typeof aData[prop] == "boolean") {
         widget[prop] = aData[prop];
       }
     }
 
     // When we normalize builtin widgets, areas have not yet been registered:
     if (aData.defaultArea &&
@@ -3291,16 +3296,19 @@ this.CustomizableUI = {
    *                  shown may pass this method a Promise, which will
    *                  prevent the view from showing until it resolves.
    *                  Additionally, if the promise resolves to the exact
    *                  value `false`, the view will not be shown.
    * - onViewHiding(aEvt): Only useful for views; a function that will be
    *                  invoked when a user hides your view.
    * - tooltiptext:   string to use for the tooltip of the widget
    * - label:         string to use for the label of the widget
+   * - localized:     If true, or undefined, attempt to retrieve the
+   *                  widget's string properties from the customizable
+   *                  widgets string bundle.
    * - removable:     whether the widget is removable (optional, default: true)
    *                  NB: if you specify false here, you must provide a
    *                  defaultArea, too.
    * - overflows:     whether widget can overflow when in an overflowable
    *                  toolbar (optional, default: true)
    * - defaultArea:   default area to add the widget to
    *                  (optional, default: none; required if non-removable)
    * - shortcutId:    id of an element that has a shortcut for this widget

--- a/browser/components/extensions/ext-browserAction.js
+++ b/browser/components/extensions/ext-browserAction.js
@@ -134,16 +134,20 @@ this.browserAction = class extends Exten
       id: this.id,
       viewId: this.viewId,
       type: "view",
       removable: true,
       label: this.defaults.title || this.extension.name,
       tooltiptext: this.defaults.title || "",
       defaultArea: this.defaults.area,
 
+      // Don't attempt to load properties from the built-in widget string
+      // bundle.
+      localized: false,
+
       onBeforeCreated: document => {
         let view = document.createElementNS(XUL_NS, "panelview");
         view.id = this.viewId;
         view.setAttribute("flex", "1");
         view.setAttribute("extension", true);
 
         document.getElementById("PanelUI-multiView").appendChild(view);
         document.addEventListener("popupshowing", this);