Revert of Prevent inherited style from propagating into a plugin placeholder.

Source/core/html/shadow/PluginPlaceholderElement.js

 // Copyright 2014 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.
 
 'use strict';
 
 installClass('PluginPlaceholderElement', function(PluginPlaceholderElementPrototype) {
     // FIXME: Load this from a .css file.
     var styleSource =
         '#plugin-placeholder {' +
-        '    all: initial;' +
         '    width: 100%;' +
         '    height: 100%;' +
         '    overflow: hidden;' +
         '    display: flex;' +
         '    align-items: center;' +
         '    background: gray;' +
         '    font: 12px -webkit-control;' +
         '}' +
         '#plugin-placeholder-content {' +
         '    text-align: center;' +
@@ skipping 17 matching lines @@
         this.appendChild(contentElement);
 
         this.messageElement = messageElement;
     };
 
     Object.defineProperty(PluginPlaceholderElementPrototype, 'message', {
         get: function() { return this.messageElement.textContent; },
         set: function(message) { this.messageElement.textContent = message; },
     });
 });