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

chrome/browser/resources/settings/internet_page/internet_detail_page.html

 <link rel="import" href="chrome://resources/cr_elements/cr_expand_button/cr_expand_button.html">
 <link rel="import" href="chrome://resources/cr_elements/icons.html">
 <link rel="import" href="chrome://resources/cr_elements/network/cr_network_icon.html">
 <link rel="import" href="chrome://resources/cr_elements/network/cr_onc_types.html">
 <link rel="import" href="chrome://resources/cr_elements/policy/cr_policy_network_behavior.html">
 <link rel="import" href="chrome://resources/cr_elements/policy/cr_policy_network_indicator.html">
 <link rel="import" href="chrome://resources/cr_elements/policy/cr_policy_pref_indicator.html">
 <link rel="import" href="chrome://resources/html/i18n_behavior.html">
 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-collapse/iron-collapse.html">
@@ skipping 26 matching lines @@
         margin: 10px 0;
       }
 
       iron-icon {
         -webkit-margin-end: 10px;
       }
 
       paper-toggle-button,
       cr-policy-network-indicator,
       cr-policy-pref-indicator {
-        -webkit-margin-start: var(--checkbox-spacing);
+        -webkit-margin-start: var(--settings-control-spacing);
       }
 
       /* Use <span> for subtitles so as not to interfere with
        * settings-box:first-of-type. */
       span.subtitle {
         font-weight: 700;
         padding: 20px;
       }
 
       .advanced {
@@ skipping 216 matching lines @@
                 on-proxy-change="onProxyChange_"
                 network-properties="[[networkProperties]]">
             </network-proxy>
           </template>
         </div>
       </iron-collapse>
     </template>
   </template>
   <script src="internet_detail_page.js"></script>
 </dom-module>