MD Settings: Align rows underneath settings-checkboxes with the settings-checkbox labels

chrome/browser/resources/settings/controls/settings_checkbox.html

 <link rel="import" href="chrome://resources/polymer/v1_0/polymer/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-checkbox/paper-checkbox.html">
 <link rel="import" href="chrome://resources/cr_elements/cr_events/cr_events.html">
 <link rel="import" href="chrome://resources/cr_elements/policy/cr_policy_pref_behavior.html">
 <link rel="import" href="chrome://resources/cr_elements/policy/cr_policy_pref_indicator.html">
 <link rel="import" href="chrome://md-settings/pref_tracker/pref_tracker.html">
 <link rel="import" href="chrome://md-settings/settings_shared_css.html">
 
 <dom-module id="settings-checkbox">
   <link rel="import" type="css" href="chrome://resources/cr_elements/shared.css">
   <template>
     <style is="custom-style" include="settings-shared">
       :host {
         align-items: center;
         display: flex;
         min-height: 40px;
       }
 
       paper-checkbox {
-        --paper-checkbox-label-spacing: 18px;
-        --paper-checkbox-size: 16px;
+        --paper-checkbox-label-spacing: var(--checkbox-spacing);
+        --paper-checkbox-size: var(--checkbox-size);
         --paper-checkbox-checked-color: var(--google-blue-500);
         --paper-checkbox-unchecked-color: #969696;
-        -webkit-margin-start: 2px;
+        -webkit-margin-start: var(--checkbox-margin-start);
       }
 
       .secondary {
         @apply(--settings-secondary);
       }
     </style>
     <cr-events id="events"></cr-events>
     <settings-pref-tracker pref="[[pref]]"></settings-pref-tracker>
 
     <div class="layout horizontal center">
       <paper-checkbox id="checkbox" checked="{{checked}}"
           disabled="[[checkboxDisabled_(disabled, pref)]]">
         <div>[[label]]</div>
         <div class="secondary">[[subLabel]]</div>
       </paper-checkbox>
       <template is="dom-if" if="[[pref.policySource]]">
         <cr-policy-pref-indicator pref="[[pref]]"></cr-policy-pref-indicator>
       </template>
     </div>
   </template>
   <script src="settings_checkbox.js"></script>
 </dom-module>