MD Settings: Bring <settings-dialog> closer to dialog spec.

chrome/browser/resources/settings/settings_shared_css.html

 <!-- Common styles for Material Design settings. -->
 <dom-module id="settings-shared">
   <template>
     <style>
       :root {
         --checkbox-margin-start: 2px;
         --checkbox-size: 16px;
         --checkbox-spacing: 18px;
         --iron-icon-fill-color: var(--paper-grey-600);
         --iron-icon-height: 20px;
@@ skipping 36 matching lines @@
         min-height: var(--settings-row-min-height);
       }
 
       iron-icon[icon=check],
       iron-icon[icon=done] {
        --iron-icon-fill-color: var(--google-green-500);
       }
 
       paper-button {
         margin: 0;
-        min-width: auto;
       }
 
       paper-button[toggles][active] {
         background-color: var(--paper-grey-300);
       }
 
       span ~ a {
         -webkit-margin-start: 4px;
       }
 
@@ skipping 185 matching lines @@
 
       .settings-checkbox-spacer {
         -webkit-margin-start: calc(
             var(--checkbox-margin-start) +
             var(--checkbox-size) +
             var(--checkbox-spacing));
       }
     </style>
   </template>
 </dom-module>