[MD settings] use arrow-forward to switch direction in rtl

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 {
     /* Some colors use non-MD colors.  These custom colors are specified by
      * UX design (bettes@). */
 
     --settings-actionable: var(--cr-actionable);
 
     --settings-background-color: rgb(241, 241, 241);
     --settings-box-row-padding: 20px;
     --settings-card-max-width: 640px;
     --settings-disabled-opacity: .65;
     --settings-error-color: var(--paper-red-700);
 
+    --settings-icon-ripple-size: 36px;
+    --settings-icon-size: 20px;
+
     --settings-list-frame-padding: {
       -webkit-padding-end: var(--settings-box-row-padding);
       -webkit-padding-start: 56px;
       padding-bottom: 0;
       padding-top: 0;
     }
 
     --settings-nav-grey: rgb(90, 90, 90);
 
     --settings-page-vertical-margin: 21px;
@@ skipping 20 matching lines @@
       height: 16px;
       top: -2px;
       width: 16px;
     };
     --settings-toggle-color: var(--google-blue-500);
 
     --checkbox-margin-start: 2px;
     --checkbox-size: 16px;
     --checkbox-spacing: 18px;
     --iron-icon-fill-color: var(--paper-grey-600);
-    --iron-icon-height: 20px;
-    --iron-icon-width: 20px;
+    --iron-icon-height: var(--settings-icon-size);
+    --iron-icon-width: var(--settings-icon-size);
     --paper-checkbox-label-color: inherit;
     --paper-dialog-color: inherit;
     --paper-icon-button: {
-      height: 36px;
-      width: 36px;
+      height: var(--settings-icon-ripple-size);
+      width: var(--settings-icon-ripple-size);
     };
     --paper-input-container-input: {
       color: inherit;
       font-size: inherit;
       font-weight: inherit;
       vertical-align: baseline;
     };
     --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>