--- a/browser/base/content/browser-sidebar.js
+++ b/browser/base/content/browser-sidebar.js
@@ -10,18 +10,18 @@
  * xul:broadcaster element with the specified ID.
  * The following attributes on that element may be used and/or modified:
  *  - id           (required) the string to match commandID. The convention
  *                 is to use this naming scheme: 'view<sidebar-name>Sidebar'.
  *  - sidebarurl   (required) specifies the URL to load in this sidebar.
  *  - sidebartitle or label (in that order) specify the title to
  *                 display on the sidebar.
  *  - checked      indicates whether the sidebar is currently displayed.
- *                 Note that toggleSidebar updates this attribute when
- *                 it changes the sidebar's visibility.
+ *                 Note that this attribute is updated when
+ *                 the sidebar's visibility is changed.
  *  - group        this attribute must be set to "sidebar".
  */
 var SidebarUI = {
   // Avoid getting the browser element from init() to avoid triggering the
   // <browser> constructor during startup if the sidebar is hidden.
   get browser() {
     if (this._browser)
       return this._browser;
@@ -251,19 +251,16 @@ var SidebarUI = {
    * Fire a "SidebarFocused" event on the sidebar's |window| to give the sidebar
    * a chance to adjust focus as needed. An additional event is needed, because
    * we don't want to focus the sidebar when it's opened on startup or in a new
    * window, only when the user opens the sidebar.
    */
   _fireFocusedEvent() {
     let event = new CustomEvent("SidebarFocused", {bubbles: true});
     this.browser.contentWindow.dispatchEvent(event);
-
-    // Run the original function for backwards compatibility.
-    fireSidebarFocusedEvent();
   },
 
   /**
    * True if the sidebar is currently open.
    */
   get isOpen() {
     return !this._box.hidden;
   },
@@ -388,19 +385,16 @@ var SidebarUI = {
       if (this.browser.contentDocument.location.href != url) {
         this.browser.addEventListener("load", event => {
 
           // We're handling the 'load' event before it bubbles up to the usual
           // (non-capturing) event handlers. Let it bubble up before firing the
           // SidebarFocused event.
           setTimeout(() => this._fireFocusedEvent(), 0);
 
-          // Run the original function for backwards compatibility.
-          sidebarOnLoad(event);
-
           resolve();
 
           // Now that the currentId is updated, fire a show event.
           this._fireShowEvent();
         }, {capture: true, once: true});
       } else {
         // Older code handled this case, so we do it too.
         this._fireFocusedEvent();
@@ -464,42 +458,8 @@ var SidebarUI = {
 
 // Add getters related to the position here, since we will want them
 // available for both startDelayedLoad and init.
 XPCOMUtils.defineLazyPreferenceGetter(SidebarUI, "_positionStart",
   SidebarUI.POSITION_START_PREF, true, SidebarUI.setPosition.bind(SidebarUI));
 XPCOMUtils.defineLazyGetter(SidebarUI, "isRTL", () => {
   return getComputedStyle(document.documentElement).direction == "rtl";
 });
-
-/**
- * This exists for backwards compatibility - it will be called once a sidebar is
- * ready, following any request to show it.
- *
- * @deprecated
- */
-function fireSidebarFocusedEvent() {}
-
-/**
- * This exists for backwards compatibility - it gets called when a sidebar has
- * been loaded.
- *
- * @deprecated
- */
-function sidebarOnLoad(event) {}
-
-/**
- * This exists for backwards compatibility, and is equivilent to
- * SidebarUI.toggle() without the forceOpen param. With forceOpen set to true,
- * it is equivalent to SidebarUI.show().
- *
- * @deprecated
- */
-function toggleSidebar(commandID, forceOpen = false) {
-  Deprecated.warning("toggleSidebar() is deprecated, please use SidebarUI.toggle() or SidebarUI.show() instead",
-                     "https://developer.mozilla.org/en-US/Add-ons/Code_snippets/Sidebar");
-
-  if (forceOpen) {
-    SidebarUI.show(commandID);
-  } else {
-    SidebarUI.toggle(commandID);
-  }
-}