PDF: Delete non-material viewer

chrome/browser/resources/pdf/elements/viewer-button/viewer-button.css

-/* Copyright 2013 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. */
-
-#icon {
-  background-position: center center;
-  background-repeat: no-repeat;
-  background-size: 100% 100%;
-  height: 100%;
-  width: 100%;
-}
-
-:host {
-  -webkit-user-select: none;
-  background-image: linear-gradient(rgb(60, 80, 119), rgb(15, 24, 41));
-  border: 1px solid rgb(11, 9, 16);
-  cursor: default;
-  display: inline-block;
-  height: 36px;
-  margin: 0;
-  pointer-events: all;
-  width: 43px;
-}
-
-:host(:focus:host) {
-  outline: none;
-}
-
-:host(:hover:host) {
-  background-image: linear-gradient(rgb(73, 102, 155), rgb(32, 52, 95));
-}
-
-:host(.latchable.polymer-selected:host),
-:host(:active:host) {
-  background-color: rgb(75, 103, 156);
-  background-image: none;
-}