DOMUI Prefs: Add inline buttons for setting the default search engine

chrome/browser/resources/options/options_page.css

 body {
   -webkit-user-select: none;
   cursor: default;
   font-size: 100%;
 }
 
 #settings-title {
   -webkit-padding-end: 24px;
   color: #53637d;
   font-size: 200%;
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 list > [editing] [editmode=false] {
   display: none;
 }
 
 list > [editing] input:invalid {
   /* TODO(stuartmorgan): Replace with validity badge */
   background-color: pink;
 }
 
-.left-side-table {
-  display: -webkit-box;
-}
-
-.left-side-table > div:first-child {
-  -webkit-box-flex: 1;
-}
-
-.left-side-table > :last-child {
-  -webkit-padding-start: 20px;
-}
-
-.left-side-table > :last-child button {
-  width: 100%;
-}
-
 .option-name {
   padding-right: 5px;
 }
 
 html[dir=rtl].option-name {
   padding-left: 5px;
 }
 
 .favicon-cell {
   -webkit-padding-start: 20px;
@@ skipping 44 matching lines @@
 }
 
 .suboption {
   -webkit-margin-start: 16px;
 }
 
 html[os=mac] label > input[type=checkbox],
 html[os=mac] label > input[type=radio] {
   margin-top: 2px;
 }