DOMUI: Use a styled button instead of an image for the password list show/hide

chrome/browser/resources/options/search_engine_manager.css

 #searchEngineList {
   -webkit-border-radius: 2px;
   border-bottom: 1px solid #d9d9d9;
   height: auto;
 }
 
 #searchEngineList .heading {
   -webkit-border-radius: 2px;
   color: black;
   border-bottom: 1px solid #d9d9d9;
@@ skipping 71 matching lines @@
 #searchEngineList .url-column {
   display: -webkit-box;
   -webkit-box-align: center;
 }
 
 #searchEngineList .url-column :first-child {
   -webkit-box-flex: 1;
 }
 
 #searchEngineList .url-column button {
-  background-color: #aab6e1;
-  border: none;
-  border-radius: 3px;
-  color: white;
+  background: #8aaaed;
+  color: #fff;
   -webkit-margin-start: 3px;
 }
 
-#searchEngineList .url-column button:hover {
-  background-color: #9aa6d1;
-}
-
-#searchEngineList .url-column button:active {
-  background-color: #8a96c1;
-}
-
 #searchEngineList > :not(:hover):not([editing]) .url-column button {
   display: none;
 }
 /* End temporary Make Default button styling */