[MD settings] CSS var --checkbox-spacing to --settings-control-spacing

chrome/browser/resources/settings/settings_shared_css.html

 <link rel="import" href="chrome://resources/cr_elements/shared_style_css.html">
 <link rel="import" href="settings_vars_css.html">
 
 <!-- Common styles for Material Design settings. -->
 <dom-module id="settings-shared">
   <template>
     <style include="cr-shared-style">
       /* Included here so we don't have to include "iron-positioning" in every
        * stylesheet. See crbug.com/498405. */
       [hidden] {
@@ skipping 100 matching lines @@
       .settings-box .secondary-button,
       .settings-box .secondary-button {
         -webkit-margin-end: -12px;
         -webkit-margin-start: -12px;
         -webkit-padding-end: 12px;
         -webkit-padding-start: 12px;
       }
 
       paper-checkbox {
         --paper-checkbox-checked-color: var(--google-blue-500);
-        --paper-checkbox-label-spacing: var(--checkbox-spacing);
+        --paper-checkbox-label-spacing: var(--settings-control-spacing);
         --paper-checkbox-size: var(--checkbox-size);
         --paper-checkbox-unchecked-color: var(--paper-grey-600);
         -webkit-margin-start: var(--checkbox-margin-start);
       }
 
       paper-radio-button {
         --paper-radio-button-checked-color: var(--google-blue-500);
         --paper-radio-button-label-spacing: 18px;
         --paper-radio-button-unchecked-color: var(--paper-grey-600);
         -webkit-margin-start: 2px;
@@ skipping 184 matching lines @@
 
       /* Helper for a list frame to automatically avoid the separator line. */
       .vertical-list > *:not(:first-of-type) {
         border-top: var(--settings-separator-line);
       }
 
       .settings-checkbox-spacer {
         -webkit-margin-start: calc(
             var(--checkbox-margin-start) +
             var(--checkbox-size) +
-            var(--checkbox-spacing));
+            var(--settings-control-spacing));
       }
 
       .favicon-image {
         background-repeat: no-repeat;
         background-size: contain;
         height: 16px;
         width: 16px;
       }
 
       .search-bubble {
@@ skipping 26 matching lines @@
       /* Turns the arrow direction downwards, when the bubble is placed above
        * the anchor element */
       .search-bubble-innards.above::after {
         bottom: -5px;
         top: auto;
         transform: rotate(-135deg);
       }
     </style>
   </template>
 </dom-module>