Implement MediaMetadata artwork in content

content/public/common/media_metadata.cc

 // 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.
 
 #include "content/public/common/media_metadata.h"
 
 namespace content {
 
 const size_t MediaMetadata::kMaxIPCStringLength = 4 * 1024;
 
 MediaMetadata::MediaMetadata() = default;
 
 MediaMetadata::~MediaMetadata() = default;
 
 bool MediaMetadata::operator==(const MediaMetadata& other) const {
-  return title == other.title && artist == other.artist && album == other.album;
+  return title == other.title && artist == other.artist &&
+      album == other.album && artwork == other.artwork;
 }
 
 bool MediaMetadata::operator!=(const MediaMetadata& other) const {
   return !this->operator==(other);
 }
 
 }  // namespace content