[MD settings] moving dialog css to shared to use in OnStartup and Reset settings

chrome/browser/resources/settings/on_startup_page/startup_urls_page.html

 <link rel="import" href="chrome://resources/polymer/v1_0/polymer/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-dialog/paper-dialog.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-input/paper-input.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-item/paper-icon-item.html">
 
 <dom-module id="settings-startup-urls-page">
+  <link rel="import" type="css" href="chrome://md-settings/settings_dialog.css">
   <link rel="import" type="css" href="chrome://md-settings/settings_shared.css">
   <link rel="import" type="css" href="on_startup_shared.css">
   <template>
     <template is="dom-repeat" items="{{prefs.session.startup_urls.value}}">
       <div class="list-item">
         <paper-icon-item>
           <iron-icon icon="image:brightness-1" item-icon></iron-icon>
           <span class="flex">[[item]]</span>
           <iron-icon on-tap="onRemoveUrlTap_" icon="clear">
           </iron-icon>
         </paper-icon-item>
       </div>
     </template>
     <div class="list-item">
       <paper-button class="link-button" on-tap="onAddPageTap_"
           i18n-content="onStartupSetPages">
       </paper-button>
     </div>
     <div class="list-item">
       <paper-button class="link-button" on-tap="onUseCurrentPagesTap_"
           i18n-content="onStartupUseCurrent">
       </paper-button>
     </div>
 
     <paper-dialog modal id="addUrlDialog" class="layout vertical">
       <div id="dialog-content">
-        <div class="dialog-title"
-            i18n-content="onStartupSetPages"></div>
-        <div class="dialog-body">
-          <paper-icon-item class="start">
-            <div i18n-content="onStartupAddPage"></div>&nbsp;
-            <paper-input class="flex" no-label-float
+        <div class="top-row">
+          <div class="title" i18n-content="onStartupAddPage"></div>
+          <paper-icon-button icon="clear" on-tap="onCancelTap_" id="close">
+          </paper-icon-button>
+        </div>
+        <div class="body">
+          <div class="explanation">
+            <paper-input class="flex" always-float-label
                 i18n-values="label:onStartupEnterUrl" value="{{newUrl}}">
             </paper-input>
-          </paper-icon-item>
+          </div>
           <div class="button-container">
             <div class="action-buttons">
               <paper-button class="cancel-button" on-tap="onCancelTap_"
                   id="cancel" i18n-content="cancel"></paper-button>
               <paper-button class="action-button" id="addUrlButton"
                   on-tap="onOkTap_" i18n-content="okButton">
               </paper-button>
             </div>
           </div>
         </div>
       </div>
     </paper-dialog>
 
   </template>
   <script src="startup_urls_page.js"></script>
 </dom-module>