MD Settings: fix settings-dialog (X) close button styles to match spec

chrome/browser/resources/settings/settings_dialog.html

 <link rel="import" href="chrome://resources/cr_elements/icons.html">
 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-dialog-behavior/paper-dialog-behavior.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-dialog-behavior/paper-dialog-shared-styles.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-icon-button/paper-icon-button.html">
 
 <dom-module id="settings-dialog">
   <template>
-    <style include="paper-dialog-shared-styles"></style>
-    <style>
+    <style include="paper-dialog-shared-styles">
       :host {
         border-radius: 2px;
       }
 
       :host ::content > * {
         /* Overrides paper-dialog-shared-styles. */
         -webkit-padding-end: 0;
         -webkit-padding-start: 0;
         margin-bottom: 0;
         margin-top: 0;
       }
 
       .title-container {
         align-items: center;
         /* TODO(dbeam): should this be a --settings-separator-line? */
         border-bottom: 1px solid rgba(0, 0, 0, 0.14);
         display: flex;
         min-height: 52px;
       }
 
       :host ::content .title {
         font-size: 114.28%; /* (16px / 14px) * 100 */
       }
 
       #close {
-        height: 20px;
-        margin: 16px;
-        padding: 0;
-        width: 20px;
+        --paper-icon-button: {
+          height: 40px;
+          width: 40px;
+        };
+        -webkit-margin-end: 6px;
+        /* <paper-icon-button> overrides --iron-icon-{height,width}, so this
+         * padding essentially reduces 40x40 to 20x20. */
+        padding: 10px;
       }
 
       .body-container {
         display: flex;
         flex-direction: column;
         max-width: 800px;
         min-width: 512px;
         /* TODO(dbeam): use <paper-dialog-scrollable> to get dividers? */
         overflow: auto;
       }
@@ skipping 43 matching lines @@
       </paper-icon-button>
     </div>
     <div class="body-container">
       <content select=".body"></content>
     </div>
     <content select=".button-container"></content>
     <content select=".footer"></content>
   </template>
   <script src="settings_dialog.js"></script>
 </dom-module>