MD WebUI: take 2 at changing all dialogs to 512px width

ui/webui/resources/cr_elements/cr_dialog/cr_dialog.html

 <link rel="import" href="chrome://resources/cr_elements/icons.html">
 <link rel="import" href="chrome://resources/html/assert.html">
 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-icon-button/paper-icon-button.html">
 
 <dom-module id="cr-dialog">
   <template>
     <style>
       :host {
         border: 0;
         border-radius: 2px;
         bottom: 0;
         color: inherit;
         padding: 0;
         top: 0;
+        width: 512px;
       }
 
       :host::backdrop {
         background-color: rgba(0, 0, 0, 0.6);
         bottom: 0;
         left: 0;
         position: fixed;
         right: 0;
         top: 0;
       }
@@ skipping 19 matching lines @@
         /* <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;
         /* TODO(dbeam): copy <paper-dialog-scrollable>'s dividers? */
         overflow: auto;
-        width: 512px;
       }
 
       :host ::content .body {
         padding-bottom: 12px;
         padding-top: 12px;
       }
 
       :host ::content .body,
       :host ::content .title {
         -webkit-padding-end: 24px;
@@ skipping 30 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="cr_dialog.js"></script>
 </dom-module>