Bug 1260460 - reset user's restore on demand preference since we're removing it from the UI. r=mconley

MozReview-Commit-ID: DHqSTh18wQu

browser/components/nsBrowserGlue.js

@@ -1804,7 +1804,7 @@ BrowserGlue.prototype = {
   },
 
   _migrateUI: function BG__migrateUI() {
-    const UI_VERSION = 36;
+    const UI_VERSION = 37;
     const BROWSER_DOCURL = "chrome://browser/content/browser.xul";
 
     let currentUIVersion;
@@ -2166,6 +2166,10 @@ BrowserGlue.prototype = {
                            "hidden");
     }
 
+    if (currentVersion < 37) {
+      Services.prefs.clearUserPref("browser.sessionstore.restore_on_demand");
+    }
+
     // Update the migration version.
     Services.prefs.setIntPref("browser.migration.version", UI_VERSION);
   },