update elements and fix some bugs

lib/src/paper-button/paper-button.html

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 @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
 The complete set of authors may be found at http://polymer.github.io/AUTHORS
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 <link rel="import" href="../polymer/polymer.html">
 <link rel="import" href="../paper-material/paper-material.html">
 <link rel="import" href="../paper-ripple/paper-ripple.html">
 <link rel="import" href="../paper-behaviors/paper-button-behavior.html">
 <link rel="import" href="../iron-flex-layout/iron-flex-layout.html">
 
 <!--
-
-Material Design: <a href="http://www.google.com/design/spec/components/buttons.html">Buttons</a>
+Material design: [Buttons](https://www.google.com/design/spec/components/buttons.html)
 
 `paper-button` is a button. When the user touches the button, a ripple effect emanates
 from the point of contact. It may be flat or raised. A raised button is styled with a
 shadow.
 
 Example:
 
     <paper-button>Flat button</paper-button>
     <paper-button raised>Raised button</paper-button>
     <paper-button noink>No ripple effect</paper-button>
@@ skipping 39 matching lines @@
 `--paper-button-ink-color` | Background color of the ripple | `Based on the button's color`
 `--paper-button` | Mixin applied to the button | `{}`
 `--paper-button-disabled` | Mixin applied to the disabled button. Note that you can also use the `paper-button[disabled]` selector | `{}`
 `--paper-button-flat-keyboard-focus` | Mixin applied to a flat button after it's been focused using the keyboard | `{}`
 `--paper-button-raised-keyboard-focus` | Mixin applied to a raised button after it's been focused using the keyboard | `{}`
 
 @demo demo/index.html
 -->
 
 <dom-module id="paper-button">
-  <template>
+  <template strip-whitespace>
 
-    <style>
+    <style include="paper-material">
       :host {
         display: inline-block;
         position: relative;
         box-sizing: border-box;
         min-width: 5.14em;
         margin: 0 0.29em;
         background: transparent;
         text-align: center;
         font: inherit;
         text-transform: uppercase;
         outline-width: 0;
         border-radius: 3px;
         -moz-user-select: none;
         -ms-user-select: none;
         -webkit-user-select: none;
         user-select: none;
         cursor: pointer;
         z-index: 0;
         padding: 0.7em 0.57em;
 
         @apply(--paper-button);
       }
 
-      :host([raised]) .keyboard-focus {
+      :host([raised].keyboard-focus) {
         font-weight: bold;
         @apply(--paper-button-raised-keyboard-focus);
       }
 
-      :host(:not([raised])) .keyboard-focus {
+      :host(:not([raised]).keyboard-focus) {
         font-weight: bold;
         @apply(--paper-button-flat-keyboard-focus);
       }
 
       :host([disabled]) {
         background: #eaeaea;
         color: #a8a8a8;
         cursor: auto;
         pointer-events: none;
 
         @apply(--paper-button-disabled);
       }
 
-      :host([noink]) paper-ripple {
-        display: none;
-      }
-
       paper-ripple {
         color: var(--paper-button-ink-color);
       }
 
-      paper-material {
-        border-radius: inherit;
-        @apply(--layout-fit);
-      }
-
-      .content > ::content * {
+      :host > ::content * {
         text-transform: inherit;
       }
     </style>
-
-    <paper-ripple></paper-ripple>
-
-    <paper-material class$="[[_computeContentClass(receivedFocusFromKeyboard)]]" elevation="[[_elevation]]" animated></paper-material>
-
     <content></content>
-
   </template>
 </dom-module>
 
 <script>
   Polymer({
     is: 'paper-button',
 
     behaviors: [
       Polymer.PaperButtonBehavior
     ],
 
     properties: {
       /**
        * If true, the button should be styled with a shadow.
        */
       raised: {
         type: Boolean,
         reflectToAttribute: true,
         value: false,
         observer: '_calculateElevation'
       }
     },
 
     _calculateElevation: function() {
       if (!this.raised) {
-        this._elevation = 0;
+        this.elevation = 0;
       } else {
         Polymer.PaperButtonBehaviorImpl._calculateElevation.apply(this);
       }
-    },
-
-    _computeContentClass: function(receivedFocusFromKeyboard) {
-      var className = 'content ';
-      if (receivedFocusFromKeyboard) {
-        className += ' keyboard-focus';
-      }
-      return className;
     }
   });
 </script>