MD Settings: Fix size and padding of expand button

ui/webui/resources/cr_elements/shared_style_css.html

 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/cr_elements/shared_vars_css.html">
 
 <!-- Common styles for Material Design WebUI. Included directly in
   settings_shared_css.html. -->
 <dom-module id="cr-shared-style">
   <template>
     <style>
       /* Chrome spinners should be blue. */
       paper-spinner {
@@ skipping 23 matching lines @@
 
       .action-button,
       .cancel-button {
         font-weight: 500;
       }
 
       [actionable] {
         @apply(--cr-actionable);
       }
 
+      button[is='paper-icon-button-light'] {
+        @apply(--cr-paper-icon-button-margin);
+        background-position: center;
+        background-repeat: no-repeat;
+        background-size: var(--cr-icon-size);
+        flex-shrink: 0;
+        height: var(--cr-icon-ripple-size);
+        width: var(--cr-icon-ripple-size);
+      }
+
       button[is='paper-icon-button-light'].subpage-arrow {
         background-image: url(../images/arrow_right.svg);
       }
 
       button[is='paper-icon-button-light'].icon-external {
         background-image: url(../images/open_in_new.svg);
       }
 
       .subpage-arrow,
       .icon-external {
         display: none;
       }
 
+      paper-icon-button.subpage-arrow {
+        background-image: url(../images/arrow_right.svg);
+      }
+
       [actionable] :-webkit-any(.subpage-arrow, .icon-external),
       [actionable]:-webkit-any(.subpage-arrow, .icon-external) {
         display: block;
       }
 
       [scrollable] {
         border-color: transparent;
         border-style: solid;
         border-width: 1px 0;
         overflow-y: auto;
@@ skipping 21 matching lines @@
       [selectable]:focus,
       [selectable] > :focus {
         @apply(--cr-selectable-focus);
       }
       [selectable] > * {
         @apply(--cr-actionable);
       }
     </style>
   </template>
 </dom-module>