Remove third_party/polymer from .gitignore

third_party/polymer/v1_0/components/paper-input/paper-input-addon-behavior.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">
-
-<script>
-
-  /**
-   * Use `Polymer.PaperInputAddonBehavior` to implement an add-on for `<paper-input-container>`. A
-   * add-on appears below the input, and may display information based on the input value and
-   * validity such as a character counter or an error message.
-   * @polymerBehavior
-   */
-  Polymer.PaperInputAddonBehavior = {
-
-    hostAttributes: {
-      'add-on': ''
-    },
-
-    attached: function() {
-      this.fire('addon-attached');
-    },
-
-    /**
-     * The function called by `<paper-input-container>` when the input value or validity changes.
-     * @param {{
-     *   inputElement: (Node|undefined),
-     *   value: (string|undefined),
-     *   invalid: (boolean|undefined)
-     * }} state All properties are optional -
-     *     inputElement: The input element.
-     *     value: The input value.
-     *     invalid: True if the input value is invalid.
-     */
-    update: function(state) {
-    }
-
-  };
-
-</script>