Remove third_party/polymer from .gitignore

third_party/polymer/v1_0/components/paper-dialog-behavior/paper-dialog-common.css

-/*
-@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
-*/
-
-:host {
-  display: block;
-  margin: 24px 40px;
-
-  background: var(--paper-dialog-background-color, --primary-background-color);
-  color: var(--paper-dialog-color, --primary-text-color);
-
-  @apply(--layout-scroll);
-  @apply(--paper-font-body1);
-  @apply(--shadow-elevation-16dp);
-  @apply(--paper-dialog);
-}
-
-:host > ::content > * {
-  margin-top: 20px;
-  padding: 0 24px;
-}
-
-:host > ::content > .no-padding {
-  padding: 0;
-}
-
-:host > ::content > *:first-child {
-  margin-top: 24px;
-}
-
-:host > ::content > *:last-child {
-  margin-bottom: 24px;
-}
-
-:host > ::content h2 {
-  position: relative;
-  margin: 0;
-  @apply(--paper-font-title);
-
-  @apply(--paper-dialog-title);
-}
-
-:host > ::content .buttons {
-  position: relative;
-  padding: 8px 8px 8px 24px;
-  margin: 0;
-
-  color: var(--paper-dialog-button-color, --default-primary-color);
-
-  @apply(--layout-horizontal);
-  @apply(--layout-end-justified);
-}