Bug 1064304 - Pre: Align PrefUtils.putStringSet docstring and reality. r=rnewman

mobile/android/base/preferences/MultiChoicePreference.java

@@ -219,7 +219,7 @@ class MultiChoicePreference extends DialogPreference implements DialogInterface.
     protected boolean persist(SharedPreferences.Editor edit) {
         if (isPersistent()) {
             Set<String> vals = getValues();
-            PrefUtils.putStringSet(edit, getKey(), vals);
+            PrefUtils.putStringSet(edit, getKey(), vals).apply();;
             return true;
         }
 

mobile/android/base/util/PrefUtils.java

@@ -54,19 +54,27 @@ public class PrefUtils {
         return new HashSet<String>();
     }
 
-    // Cross version compatible way to save a string set to a pref.
-    // NOTE: The editor that is passed in will not commit the transaction for you. It is up to callers to commit
-    //       when they are done with any other changes to the database.
-    public static SharedPreferences.Editor putStringSet(final SharedPreferences.Editor edit,
+    /**
+     * Cross version compatible way to save a set of strings.
+     * <p>
+     * This method <b>does not commit</b> any transaction. It is up to callers
+     * to commit.
+     *
+     * @param editor to write to.
+     * @param key to write.
+     * @param vals comprising string set.
+     * @return
+     */
+    public static SharedPreferences.Editor putStringSet(final SharedPreferences.Editor editor,
                                     final String key,
                                     final Set<String> vals) {
         if (Versions.preHC) {
             final JSONArray json = new JSONArray(vals);
-            edit.putString(key, json.toString()).apply();
+            editor.putString(key, json.toString());
         } else {
-            edit.putStringSet(key, vals).apply();
+            editor.putStringSet(key, vals);
         }
 
-        return edit;
+        return editor;
     }
 }