Import Polymer 0.8 and several key elements.

third_party/polymer/v0_8/components/paper-checkbox/paper-checkbox.html

Index: third_party/polymer/v0_8/components/paper-checkbox/paper-checkbox.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.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">
+<link rel="import" href="../paper-ripple/paper-ripple.html">
+<link rel="import" href="../paper-styles/default-theme.html">
+
+<!--
+`paper-checkbox` is a button that can be either checked or unchecked.  User
+can tap the checkbox to check or uncheck it.  Usually you use checkboxes
+to allow user to select multiple options from a set.  If you have a single
+ON/OFF option, avoid using a single checkbox and use `paper-toggle-button`
+instead.
+
+Example:
+
+    <paper-checkbox>label</paper-checkbox>
+
+    <paper-checkbox checked> label</paper-checkbox>
+
+Styling a checkbox:
+
+<style is="x-style">
+  * {
+    /* Unhecked state colors. */
+    --paper-checkbox-unchecked-color: #5a5a5a;
+    --paper-checkbox-unchecked-ink-color: #5a5a5a;
+
+    /* Checked state colors. */
+    --paper-checkbox-checked-color: #009688;
+    --paper-checkbox-checked-ink-color: #009688;
+  }
+</style>
+
+@group Paper Elements
+@class paper-checkbox
+-->
+
+/* TODO: This needs to use core-focusable when it's ready. */
+<dom-module id="paper-checkbox">
+  <style is="x-style">
+    * {
+      --paper-checkbox-unchecked-color: var(--primary-text-color);
+      --paper-checkbox-unchecked-ink-color: var(--primary-text-color);
+
+      --paper-checkbox-checked-color: var(--default-primary-color);
+      --paper-checkbox-checked-ink-color: var(--default-primary-color);
+    }
+  </style>
+
+  <link rel="import" type="css" href="paper-checkbox.css">
+
+  <template>
+
+    <div id="checkboxContainer">
+      <paper-ripple id="ink" class="circle" recenters checked$="[[checked]]"></paper-ripple>
+      <div id="checkbox" class$="[[_computeCheckboxClass(checked)]]">
+        <div id="checkmark" class$="[[_computeCheckmarkClass(checked)]]"></div>
+      </div>
+    </div>
+
+    <div id="checkboxLabel" aria-hidden="true"><content></content></div>
+
+  </template>
+</dom-module>
+
+<script>
+  Polymer({
+    is: 'paper-checkbox',
+
+    // The custom properties shim is currently an opt-in feature.
+    enableCustomStyleProperties: true,
+
+    hostAttributes: {
+      role: 'checkbox',
+      'aria-checked': false,
+      tabindex: 0
+    },
+
+    properties: {
+      /**
+       * Fired when the checked state changes due to user interaction.
+       *
+       * @event change
+       */
+
+      /**
+       * Fired when the checked state changes.
+       *
+       * @event iron-change
+       */
+
+      /**
+       * Gets or sets the state, `true` is checked and `false` is unchecked.
+       *
+       * @attribute checked
+       * @type boolean
+       * @default false
+       */
+      checked: {
+        type: Boolean,
+        value: false,
+        reflectToAttribute: true,
+        observer: '_checkedChanged'
+      },
+
+      /**
+       * If true, the user cannot interact with this element.
+       *
+       * @attribute disabled
+       * @type boolean
+       * @default false
+       */
+      disabled: {
+        type: Boolean
+      }
+    },
+
+    listeners: {
+      keydown: '_onKeyDown',
+      mousedown: '_onMouseDown'
+    },
+
+    ready: function() {
+      if (this.$.checkboxLabel.textContent == '') {
+        this.$.checkboxLabel.hidden = true;
+      } else {
+        this.setAttribute('aria-label', this.$.checkboxLabel.textContent);
+      }
+    },
+
+    _computeCheckboxClass: function(checked) {
+      if (checked) {
+        return 'checked';
+      }
+    },
+
+    _computeCheckmarkClass: function(checked) {
+      if (!checked) {
+        return 'hidden';
+      }
+    },
+
+    _onKeyDown: function(e) {
+      // Enter key.
+      if (e.keyCode === 13) {
+        this._onMouseDown();
+        e.preventDefault();
+      }
+    },
+
+    _onMouseDown: function() {
+      if (this.disabled) {
+        return;
+      }
+
+      var old = this.checked;
+      this.checked = !this.checked;
+
+      if (this.checked !== old) {
+        this.fire('iron-change');
+      }
+    },
+
+    _checkedChanged: function() {
+      this.setAttribute('aria-checked', this.checked ? 'true' : 'false');
+      this.fire('iron-change');
+    }
+  })
+</script>