Bug 1548026 - Noop download button's changed callback when unloaded. r=bzbarsky

Temporary workaround to prevent wrapper assertions in torn-down
window.

Differential Revision: https://phabricator.services.mozilla.com/D29410

--HG--
extra : moz-landing-system : lando

browser/components/downloads/content/indicator.js

@@ -50,6 +50,13 @@ const DownloadsButton = {
    */
   _customizing: false,
 
+  /**
+   * Indicates whether the button has been torn down.
+   * TODO: This is used for a temporary workaround for bug 1543537 and should be
+   * removed when fixed.
+   */
+  _uninitialized: false,
+
   /**
    * This function is called asynchronously just after window initialization.
    *
@@ -159,6 +166,9 @@ const DownloadsButton = {
   },
 
   checkForAutoHide() {
+    if (this._uninitialized) {
+      return;
+    }
     let button = this._placeholder;
     if (!this._customizing && this.autoHideDownloadsButton &&
         button && button.closest("toolbar")) {
@@ -213,6 +223,7 @@ const DownloadsButton = {
   },
 
   uninit() {
+    this._uninitialized = true;
     CustomizableUI.removeListener(this);
   },