Revert "Bug 1898356 - go back one page arrow (button) turns grey after clearing browsing & download history. r=hsohaney" for causing bc failures @ browser_purgehistory_clears_sh.js

This reverts commit 54aaf25.

Author: amarc-mozilla

browser/base/content/browser.js

@@ -1025,21 +1025,16 @@ const gClickAndHoldListenersOnElement = {
   },
 };
 
-// See bug 1898356 - Navigation buttons aren't being properly disabled
-// when clearing the history. This is due that this callback is called
-// before the panel is closed. By setting "wasdisabled" attribute instead
-// of "disabled" attribute, we are sort of "lying" to `_updateMenuAndCommandState`
-// that they where previously disabled, so it will not enable them.
 const gSessionHistoryObserver = {
   observe(subject, topic) {
     if (topic != "browser:purge-session-history") {
       return;
     }
 
     var backCommand = document.getElementById("Browser:Back");
-    backCommand.setAttribute("wasdisabled", "true");
+    backCommand.setAttribute("disabled", "true");
     var fwdCommand = document.getElementById("Browser:Forward");
-    fwdCommand.setAttribute("wasdisabled", "true");
+    fwdCommand.setAttribute("disabled", "true");
 
     // Clear undo history of the URL bar
     gURLBar.editor.clearUndoRedo();

browser/base/content/test/backforward/browser.toml

@@ -3,5 +3,3 @@
 ["browser_history_menu.js"]
 fail-if = ["a11y_checks"] # Bug 1854233 navigator-toolbox may not be focusable
 https_first_disabled = true
-
-["browser_history_menu_clear.js"]