Relanding: MD Settings: Adding some unit tests for <settings-main>.

chrome/browser/resources/settings/settings_main/settings_main.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/html/promise_resolver.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-icon/iron-icon.html">
 <link rel="import" href="/about_page/about_page.html">
 <link rel="import" href="/advanced_page/advanced_page.html">
 <link rel="import" href="/basic_page/basic_page.html">
 <link rel="import" href="/route.html">
 <link rel="import" href="/settings_page/main_page_behavior.html">
 <link rel="import" href="/settings_vars_css.html">
 
 <dom-module id="settings-main">
   <template>
@@ skipping 19 matching lines @@
       }
 
       #toggleSpacer {
         padding-top: 33px;  /* Part of a 48px spacer (33px + 12px + 3px). */
       }
 
       iron-icon {
         -webkit-margin-start: 16px;
       }
 
-      #no-search-results {
+      #noSearchResults {
         align-items: center;
         display: flex;
         flex-direction: column;
         margin-top: 80px;
       }
 
-      #no-search-results div:first-child {
+      #noSearchResults div:first-child {
         font-size: 120%;
         margin-bottom: 10px;
       }
     </style>
     <content select="paper-icon-button"></content>
-    <div id="no-search-results" hidden$="[[!showNoResultsFound_]]">
+    <div id="noSearchResults" hidden$="[[!showNoResultsFound_]]">
       <div>$i18n{searchNoResults}</div>
       <div>$i18nRaw{searchNoResultsHelp}</div>
     </div>
     <template is="dom-if" if="[[showPages_.basic]]">
       <settings-basic-page prefs="{{prefs}}" current-route="{{currentRoute}}"
           page-visibility="[[pageVisibility]]">
       </settings-basic-page>
     </template>
     <template is="dom-if"
         if="[[showAdvancedSettings_(pageVisibility.advancedSettings)]]">
@@ skipping 16 matching lines @@
     </template>
     <template is="dom-if" if="[[showPages_.about]]">
       <settings-about-page current-route="{{currentRoute}}">
       </settings-about-page>
     </template>
     <div id="overscroll" style="padding-bottom: [[overscroll_]]px"></div>
   </template>
   <script src="settings_main.js"></script>
   <script src="/search_settings.js"></script>
 </dom-module>