[MD settings] icons for clickable rows

chrome/browser/resources/settings/settings_vars_css.html

 <link rel="import" href="chrome://resources/cr_elements/shared_vars_css.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-styles/color.html">
 
 <!-- Common css variables for Material Design settings. -->
 <style is="custom-style">
   /* We keep our vars in sort order, though some vars must be defined prior to
    * others. The --settings-* vars are defined explicitly prior to the --paper-*
    * and --iron-* vars.
    */
   :root {
@@ skipping 43 matching lines @@
     };
     --settings-toggle-color: var(--google-blue-500);
   }
 
   :root {
     --checkbox-margin-start: 2px;
     --checkbox-size: 16px;
     --checkbox-spacing: 18px;
     --iron-icon-fill-color: var(--paper-grey-600);
     --iron-icon-height: 20px;
-    --iron-icon-spacing: 16px;
     --iron-icon-width: 20px;
     --paper-checkbox-label-color: inherit;
     --paper-dialog-color: inherit;
     --paper-icon-button: {
       height: 36px;
       width: 36px;
     };
     --paper-input-max-width: 264px;
     --paper-item: {
       font-size: inherit;
     };
     --paper-radio-button-label-color: inherit;
     --paper-radio-group-item-padding: 0;
 
     --paper-toggle-button-checked-bar: var(--settings-toggle-bar-size);
     --paper-toggle-button-checked-bar-color: var(--settings-toggle-color);
     --paper-toggle-button-checked-button: {
       @apply(--settings-toggle-button-size);
       transform: translate(14px, 0);
     };
     --paper-toggle-button-checked-button-color: var(--settings-toggle-color);
     --paper-toggle-button-label-spacing: 0;
     --paper-toggle-button-unchecked-bar: var(--settings-toggle-bar-size);
     --paper-toggle-button-unchecked-button: var(--settings-toggle-button-size);
   }
 </style>