code: function (oldContext, newContext) {
              var changes = [];
  
              _.each(this._scopes, function (scope) {
                  var changedInScope = scope.contextChanged(oldContext, newContext);
                  if (changedInScope) {
                      changes.push(changedInScope);
                  }
              });
  
              changes = _.union.apply(null, changes);
              if (changes.length > 0) {
                  this._triggerChange({
                      ids: changes
                  });
              }
          }
docs: Signals the context change to all the scopes within the preferences
  layer.  PreferencesManager is in charge of computing the context and
  signaling the changes to PreferencesSystem.
  
  @param {{path: string, language: string}} oldContext Old context
  @param {{path: string, language: string}} newContext New context