Remove the unmaintained performance monitor.

chrome/browser/resources/performance_monitor/chart.css

-/* Copyright (c) 2012 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. */
-
-/* "Performance" title */
-h1 {
-  -webkit-margin-after: 1em;
-  -webkit-margin-before: 21px;
-  -webkit-margin-start: 23px;
-  -webkit-user-select: none;
-  color: rgb(92, 97, 102);
-  display: block;
-  font-size: 1.5em;
-  font-weight: normal;
-  line-height: 1;
-}
-
-/* Settings panel category headings */
-h2 {
-  -webkit-user-select: none;
-  border: 0;
-  color: inherit;
-  cursor: pointer;
-  font: inherit;
-  font-size: 1.2em;
-  font-weight: normal;
-  line-height: 1;
-  margin: 0;
-}
-
-/* Settings panel subcategory headings */
-h3 {
-  -webkit-margin-after: 3px;
-  -webkit-user-select: none;
-  color: rgb(48, 57, 66);
-  font-size: 1em;
-  font-weight: normal;
-  line-height: 1;
-}
-
-/* Axis labels */
-h4 {
-  -webkit-margin-after: 0;
-  -webkit-margin-before: 0;
-  color: rgb(92, 97, 102);
-  font-size: 12px;
-  font-weight: bold;
-  line-height: 12px;
-}
-
-.accordion {
-  left: 0;
-  position: fixed;
-  top: 0;
-  width: 200px;
-}
-
-details {
-  margin-bottom: 20px;
-}
-
-summary {
-  -webkit-margin-start: 23px;
-  -webkit-user-select: none;
-  color: #777;
-  cursor: default;
-}
-
-summary:focus {
-  outline: 0;
-}
-
-summary::after {
-  background: white;
-  content: '';
-  height: 32px;
-  left: 0;
-  margin-top: -23px;
-  position: absolute;
-  width: 6px;
-}
-
-summary:hover {
-  color: rgb(70, 78, 90);
-}
-
-details[open] summary::after {
-  background: #555;
-}
-
-details[open] summary {
-  color: #333;
-}
-
-details summary::-webkit-details-marker {
-  display: none;
-}
-
-.accordion-contents {
-  -webkit-margin-start: 35px;
-  color: #555;
-}
-
-.spacer {
-  -webkit-box-flex: 1;
-}
-
-input[type='radio']:checked+span {
-  color: #222;
-}
-
-input[type='checkbox']:checked+span {
-  color: #222;
-}
-
-.input-label:hover {
-  color: #222;
-}
-
-#warnings-box {
-  -webkit-margin-after: 15px;
-  -webkit-margin-before: 21px;
-  display: none;
-  text-align: center;
-}
-
-#warnings-text {
-  background-color: pink;
-  box-shadow: 0 1px 10px 1px rgba(0, 0, 0, 0.2), 0 1px 3px rgba(0, 0, 0, 0.15);
-  display: inline-block;
-  max-width: 1000px;
-  padding: 6px;
-}
-
-.warning {
-  display: none;
-}
-
-#time-shift-category {
-  display: inline-block;
-}
-
-#charts {
-  -webkit-margin-start: 200px;
-  min-width: 800px;
-  width: 80%;
-}
-
-.chart {
-  position: relative;
-}
-
-.grid {
-  -webkit-margin-after: 15px;
-  height: 500px;
-  position: relative;
-}
-
-/* This is necessary since rotation does not work well with text elements, which
- * have an adjustable size. Calculations for each section are listed. */
-.yaxis-label-container {
-  -webkit-transform: rotate(-90deg);
-  left: -238px;  /* .grid height / 2 - h4 line-height */
-  position: absolute;
-  text-align: center;
-  top: 244px;    /* .grid height / 2 - .yaxis-label line-height / 2 */
-  width: 500px;  /* .grid height */
-}
-
-.event-label {
-  background: #eee;
-  border: 1px solid;
-  font-family: Arial, sans-serif;
-  font-size: 0.7em;
-  position: absolute;
-}
-
-.horizontal-box {
-  -webkit-box-orient: horizontal;
-  display: -webkit-box;
-}
-
-h2#flag-warning {
-  display: none;
-}
-
-button {
-  -webkit-padding-end: 10px;
-  -webkit-padding-start: 10px;
-  background-color: buttonface;
-  background-image: -webkit-linear-gradient(#EDEDED, #EDEDED 38%, #DEDEDE);
-  border: 1px solid rgba(0, 0, 0, 0.25);
-  border-radius: 2px;
-  box-shadow: 0 1px 0 rgba(0, 0, 0, 0.08),
-      inset 0 1px 2px rgba(255, 255, 255, 0.75);
-  color: #444;
-  font: inherit;
-  height: 1.5em;
-  margin: 0 1px 0 0;
-  min-width: 4em;
-  text-shadow: #F0F0F0 0 1px 0;
-}
-
-button:active {
-  background-image: -webkit-linear-gradient(#e7e7e7, #e7e7e7 38%, #d7d7d7);
-  box-shadow: none;
-  text-shadow: none;
-}