Bug 1312406 and bug 1255361 - part 2: remove tab groups backup, r=Dolske

MozReview-Commit-ID: 96AFjsXE1w0

--HG--
extra : rebase_source : 43089420551d75274a99a0b663b193778cfcf52d

browser/components/nsBrowserGlue.js

@@ -1773,7 +1773,7 @@ BrowserGlue.prototype = {
   },
 
   _migrateUI: function BG__migrateUI() {
-    const UI_VERSION = 41;
+    const UI_VERSION = 42;
     const BROWSER_DOCURL = "chrome://browser/content/browser.xul";
 
     let currentUIVersion;
@@ -2101,6 +2101,12 @@ BrowserGlue.prototype = {
       Preferences.resetBranch("loop.");
     }
 
+    if (currentUIVersion < 42) {
+      let backupFile = Services.dirsvc.get("ProfD", Ci.nsIFile);
+      backupFile.append("tabgroups-session-backup.json");
+      OS.File.remove(backupFile.path, {ignoreAbsent: true}).catch(ex => Cu.reportError(ex));
+    }
+
     // Update the migration version.
     Services.prefs.setIntPref("browser.migration.version", UI_VERSION);
   },