message: Comments for polymer2-config functions.
diff: +/**
  + * @license
  + * Copyright (c) 2016 The Polymer Project Authors. All rights reserved.
  + * This code may only be used under the BSD style license found at
  + * http://polymer.github.io/LICENSE.txt
  + * The complete set of authors may be found at
  + * http://polymer.github.io/AUTHORS.txt
  + * The complete set of contributors may be found at
  + * http://polymer.github.io/CONTRIBUTORS.txt
  + * Code distributed by Google as part of the polymer project is also
  + * subject to an additional IP rights grant found at
  + * http://polymer.github.io/PATENTS.txt
  + */
  +
  import * as estree from 'estree';
  import {getIdentifierName} from '../javascript/ast-value';
  @@ -7,6 +21,10 @@ import {JavaScriptDocument} from '../javascript/javascript-document';
  import {analyzeProperties} from './analyze-properties';
  import {ScannedPolymerProperty} from './polymer-element';
  +/**
  + * Returns the object literal that defines a Polymer element configuration from
  + * a Plymer element class.
  + */
  export function getConfig(node: estree.ClassDeclaration|estree.ClassExpression):
  estree.ObjectExpression|null {
  const possibleConfigs = node.body.body.filter(
  @@ -23,18 +41,22 @@ export function getConfig(node: estree.ClassDeclaration|estree.ClassExpression):
  return null;
  }
  if (configBody.body[0].type !== 'ReturnStatement') {
  + // we only support a return statement
  return null;
  }
  const returnStatement = configBody.body[0] as estree.ReturnStatement;
  const returnValue = returnStatement.argument;
  if (!returnValue || returnValue.type !== 'ObjectExpression') {
  - // TODO: warn
  + // we only support object literals
  return null;
  }
  - return returnValue as estree.ObjectExpression;
  + return returnValue;
  }
  +/**
  + * Returns the properties defined in a Polymer config object literal.
  + */
  export function getProperties(
  node: estree.ObjectExpression,
  document: JavaScriptDocument): ScannedPolymerProperty[] {
  