Add material design toggle ripple element.

ui/file_manager/gallery/elements/gallery_toggle_button.html

+<!-- Copyright 2015 The Chromium Authors. All rights reserved.
+  -- Use of this source code is governed by a BSD-style license that can be
+  -- found in the LICENSE file.
+  -->
+
+<link rel="import" href="chrome://resources/polymer/v1_0/polymer/polymer.html">
+
+<dom-module id="gallery-toggle-button">
+  <style>
+    :host {
+      position: relative;
+    }
+
+    .ripple-container {
+      align-items: center;
+      display: flex;
+      height: 100%;
+      position: absolute;
+      width: 100%;
+    }
+
+    .ripple {
+      background-color: white;
+      height: 0;
+      margin: 0 auto;
+      opacity: 0;
+      width: 0;
+    }
+
+    .ripple.activated {
+      border-radius: 2.56%;
+      height: 60.3%;
+      opacity: 0.2;
+      width: 60.3%;
+    }
+  </style>
+  <template>
+    <div class="ripple-container" on-tap="onTapped_">
+      <div class="ripple" id="ripple"></div>
+    </div>
+    <content class="content"></content>
+  </template>
+</dom-module>
+
+<script src="gallery_toggle_button.js"></script>