Support to repeat one song in Audio Player.

ui/file_manager/audio_player/elements/repeat_button.css

+/* Copyright 2016 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. */
+
+:host {
+  border-radius: 2px;
+  cursor: pointer;
+  display: inline-block;
+  height: 32px;
+  outline: none;
+  position: relative;
+  width: 32px;
+}
+
+.repeat-all, .no-repeat {
+  background-image: -webkit-image-set(
+      url(../assets/100/player_button_repeat.png) 1x,
+      url(../assets/200/player_button_repeat.png) 2x);
+}
+
+.repeat-one {
+  background-image: -webkit-image-set(
+      url(../assets/100/player_button_repeat_one.png) 1x,
+      url(../assets/200/player_button_repeat_one.png) 2x);
+}
+
+files-toggle-ripple {
+  background-position: center;
+  background-repeat: no-repeat;
+  height: 28px;
+  left: 2px;
+  pointer-events: none;
+  position: absolute;
+  top: 2px;
+  width: 28px;
+}