DOMUI Prefs: Implement inline editability for startup pages

chrome/browser/resources/options/browser_options_page.css

 
 #startupPageManagement.settings-list > :last-child {
   border-top: 1px solid #d9d9d9;
   padding: 5px 10px;
 }
 
+.startup-page-list .title {
+  width: 40%;
+}
+
+.startup-page-list .url {
+  -webkit-box-flex: 1;
+  color: #666;
+}
+
+.startup-page-list .url input {
+  box-sizing: border-box;
+  margin: 0;
+  width: 100%;
+}
+
 #customHomePageGroup {
   display: -webkit-box;
   -webkit-box-orient: horizontal;
 }
 
 #customHomePageGroup > div {
   -webkit-padding-start: 1ex;
   -webkit-box-flex: 1;
 }
 
@@ skipping 35 matching lines @@
 #instantConfirmText {
   font-family: inherit;
   white-space: pre-wrap;
   width: 500px;
 }
 
 #instantConfirmLearnMore {
   position: absolute;
   bottom: 18px;
 }