Remove third_party/polymer from .gitignore

third_party/polymer/v1_0/components/iron-collapse/iron-collapse.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">
-
-<!--
-`iron-collapse` creates a collapsible block of content.  By default, the content
-will be collapsed.  Use `opened` or `toggle()` to show/hide the content.
-
-    <button on-click="{{toggle}}">toggle collapse</button>
-
-    <iron-collapse id="collapse">
-      <div>Content goes here...</div>
-    </iron-collapse>
-
-    ...
-
-    toggle: function() {
-      this.$.collapse.toggle();
-    }
-
-`iron-collapse` adjusts the height/width of the collapsible element to show/hide
-the content.  So avoid putting padding/margin/border on the collapsible directly,
-and instead put a div inside and style that.
-
-    <style>
-      .collapse-content {
-        padding: 15px;
-        border: 1px solid #dedede;
-      }
-    </style>
-
-    <iron-collapse>
-      <div class="collapse-content">
-        <div>Content goes here...</div>
-      </div>
-    </iron-collapse>
-
-@group Iron Elements
-@hero hero.svg
-@demo demo/index.html
-@element iron-collapse
--->
-
-<dom-module id="iron-collapse">
-
-  <style>
-
-    :host {
-      display: block;
-      transition-duration: 300ms;
-    }
-
-    :host(.iron-collapse-closed) {
-      display: none;
-    }
-
-    :host(:not(.iron-collapse-opened)) {
-      overflow: hidden;
-    }
-
-  </style>
-
-  <template>
-
-    <content></content>
-
-  </template>
-
-</dom-module>
-
-<script>
-
-  Polymer({
-
-    is: 'iron-collapse',
-
-    properties: {
-
-      /**
-       * If true, the orientation is horizontal; otherwise is vertical.
-       *
-       * @attribute horizontal
-       */
-      horizontal: {
-        type: Boolean,
-        value: false,
-        observer: '_horizontalChanged'
-      },
-
-      /**
-       * Set opened to true to show the collapse element and to false to hide it.
-       *
-       * @attribute opened
-       */
-      opened: {
-        type: Boolean,
-        value: false,
-        notify: true,
-        observer: '_openedChanged'
-      }
-
-    },
-
-    hostAttributes: {
-      role: 'group',
-      'aria-expanded': 'false'
-    },
-
-    listeners: {
-      transitionend: '_transitionEnd'
-    },
-
-    ready: function() {
-      // Avoid transition at the beginning e.g. page loads and enable
-      // transitions only after the element is rendered and ready.
-      this._enableTransition = true;
-    },
-
-    /**
-     * Toggle the opened state.
-     *
-     * @method toggle
-     */
-    toggle: function() {
-      this.opened = !this.opened;
-    },
-
-    show: function() {
-      this.toggleClass('iron-collapse-closed', false);
-      this.updateSize('auto', false);
-      var s = this._calcSize();
-      this.updateSize('0px', false);
-      // force layout to ensure transition will go
-      this.offsetHeight;
-      this.updateSize(s, true);
-    },
-
-    hide: function() {
-      this.toggleClass('iron-collapse-opened', false);
-      this.updateSize(this._calcSize(), false);
-      // force layout to ensure transition will go
-      this.offsetHeight;
-      this.updateSize('0px', true);
-    },
-
-    updateSize: function(size, animated) {
-      this.enableTransition(animated);
-      var s = this.style;
-      var nochange = s[this.dimension] === size;
-      s[this.dimension] = size;
-      if (animated && nochange) {
-        this._transitionEnd();
-      }
-    },
-
-    enableTransition: function(enabled) {
-      this.style.transitionDuration = (enabled && this._enableTransition) ? '' : '0s';
-    },
-
-    _horizontalChanged: function() {
-      this.dimension = this.horizontal ? 'width' : 'height';
-      this.style.transitionProperty = this.dimension;
-    },
-
-    _openedChanged: function() {
-      this[this.opened ? 'show' : 'hide']();
-      this.setAttribute('aria-expanded', this.opened ? 'true' : 'false');
-
-    },
-
-    _transitionEnd: function() {
-      if (this.opened) {
-        this.updateSize('auto', false);
-      }
-      this.toggleClass('iron-collapse-closed', !this.opened);
-      this.toggleClass('iron-collapse-opened', this.opened);
-      this.enableTransition(false);
-    },
-
-    _calcSize: function() {
-      return this.getBoundingClientRect()[this.dimension] + 'px';
-    },
-
-
-  });
-
-</script>