Update Polymer components.

third_party/polymer/components/iron-flex-layout/iron-flex-layout.html

 <!--
 @license
 Copyright (c) 2015 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
 -->
 
 <link rel="import" href="../polymer/polymer.html">
 
 <!--
 The `<iron-flex-layout>` component provides simple ways to use
 [CSS flexible box layout](https://developer.mozilla.org/en-US/docs/Web/Guide/CSS/Flexible_boxes),
 also known as flexbox. This component provides two different ways to use flexbox:
 
 1. [Layout classes](https://github.com/PolymerElements/iron-flex-layout/tree/master/iron-flex-layout-classes.html).
 The layout class stylesheet provides a simple set of class-based flexbox rules, that
 let you specify layout properties directly in markup. You must include this file
 in every element that needs to use them.
 
-  Sample use:
+    Sample use:
 
-      <link rel="import" href="../iron-flex-layout/iron-flex-layout-classes.html">
-      <style is="custom-style" include="iron-flex iron-flex-alignment"></style>
+    ```
+    <custom-element-demo>
+      <template>
+        <script src="../webcomponentsjs/webcomponents-lite.js"></script>
+        <next-code-block></next-code-block>
+      </template>
+    </custom-element-demo>
+    ```
 
-      <div class="layout horizontal layout-start">
-        <div>cross axis start alignment</div>
-      </div>
+    ```html
+    <link rel="import" href="iron-flex-layout-classes.html">
+    <style is="custom-style" include="iron-flex iron-flex-alignment"></style>
+    <style>
+      .test { width: 100px; }
+    </style>
+    <div class="layout horizontal center-center">
+      <div class="test">horizontal layout center alignment</div>
+    </div>
+    ```
 
 2. [Custom CSS mixins](https://github.com/PolymerElements/iron-flex-layout/blob/master/iron-flex-layout.html).
 The mixin stylesheet includes custom CSS mixins that can be applied inside a CSS rule using the `@apply` function.
 
 Please note that the old [/deep/ layout classes](https://github.com/PolymerElements/iron-flex-layout/tree/master/classes)
 are deprecated, and should not be used. To continue using layout properties
 directly in markup, please switch to using the new `dom-module`-based
 [layout classes](https://github.com/PolymerElements/iron-flex-layout/tree/master/iron-flex-layout-classes.html).
 Please note that the new version does not use `/deep/`, and therefore requires you
 to import the `dom-modules` in every element that needs to use them.
@@ skipping 57 matching lines @@
       -ms-flex-direction: column-reverse;
       -webkit-flex-direction: column-reverse;
       flex-direction: column-reverse;
     };
 
     --layout-wrap: {
       -ms-flex-wrap: wrap;
       -webkit-flex-wrap: wrap;
       flex-wrap: wrap;
     };
-    
+
     --layout-no-wrap: {
       -ms-flex-wrap: nowrap;
       -webkit-flex-wrap: nowrap;
       flex-wrap: nowrap;
     };
 
     --layout-wrap-reverse: {
       -ms-flex-wrap: wrap-reverse;
       -webkit-flex-wrap: wrap-reverse;
       flex-wrap: wrap-reverse;
@@ skipping 277 matching lines @@
     --layout-fixed-left: {
       position: fixed;
       top: 0;
       bottom: 0;
       left: 0;
     };
 
   }
 
 </style>