Change bookmark manager header to look more like settings/extensions/history.

chrome/browser/resources/bookmark_manager/css/bmm.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. */
 
 html,
 body {
   cursor: default;
   height: 100%;
   margin: 0;
   overflow: hidden;
@@ skipping 231 matching lines @@
   -webkit-border-end: 15px solid white;
   -webkit-border-start: 0;
   background-color: rgb(235, 239, 249);
   cursor: e-resize;
   width: 5px;
 <if expr="is_macosx">
   cursor: col-resize;
 </if>
 }
 
-.logo {
-  -webkit-appearance: none;
-  background: url('../images/bookmarks_section_32.png') no-repeat 50% 50%;
-  border: 0;
-  cursor: pointer;
-  float: left;
-  height: 32px;
-  margin: 10px;
-  width: 32px;
+header {
+  align-items: center;
+  display: flex;
+  min-width: 400px;
+  padding: 0 12px;
 }
 
-html:not(.focus-outline-visible) .logo:focus {
-  outline: none;
+header h2 {
+  flex: 1;
+  font-weight: normal;
 }
 
-.header form {
-  float: left;
-  margin: 14px 2px 0 2px;
-  width: 171px;
-}
-
-.header {
-  min-width: 400px;
-}
-
-html[dir=rtl] .logo,
-html[dir=rtl] .header > div,
-html[dir=rtl] .header form {
-  float: right;
+header form {
+  flex: none;
 }
 
 .tree-row.drag-on,
 .drag-on {
   background-color: hsla(214, 91%, 85%, .5);
   border: 1px solid hsl(214, 91%, 85%);
   border-radius: 3px;
   box-sizing: border-box;
 }
 
@@ skipping 41 matching lines @@
 }
 
 .summary > * {
   display: inline-block;
   font-size: 100%;
   margin: 0;
 }
 
 .summary button {
   -webkit-appearance: none;
-  -webkit-margin-start: 10px;
+  -webkit-margin-start: 16px;
   -webkit-padding-end: 11px;
   -webkit-padding-start: 0;
   background: transparent -webkit-canvas(drop-down-arrow)
               no-repeat right center;
   border: 0;
   font: inherit;
+  font-weight: bold;
   padding-bottom: 0;
   padding-top: 0;
 }
 
 html[dir=rtl] .summary button {
   background-position: left center;
 }
 
 @media (pointer:coarse) {
   list > *,
   menu > button,
   .tree-item > .tree-row {
     line-height: 28px;
   }
 
   list [editing] input,
   .tree-item [editing] input {
     padding: 3px 0;
   }
 
   .tree-row .expand-icon {
     top: 6px;
   }
 }