MD History: Add spinners when new data is loading or searching

chrome/browser/resources/md_history/history_toolbar.html

 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-flex-layout/iron-flex-layout.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-button/paper-button.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-icon-button/paper-icon-button.html">
+<link rel="import" href="chrome://resources/polymer/v1_0/paper-spinner/paper-spinner.html">
 <link rel="import" href="chrome://resources/cr_elements/cr_search_field/cr_search_field.html">
 <link rel="import" href="chrome://history/shared_style.html">
 
 <dom-module id="history-toolbar">
   <template>
     <style include="shared-style">
       :host {
         background: rgb(63, 85, 102);
         color: #fff;
         height: 56px;
@@ skipping 29 matching lines @@
 
       :host([has-sidebar]) #left-content {
         flex: 1 0 var(--side-bar-width);
       }
 
       #centered-buttons {
         flex: 0 1 var(--card-max-width);
         padding: 0 var(--card-padding-side);
       }
 
+      #right-content {
+        @apply(--layout-center);
+        @apply(--layout-horizontal);
+        justify-content: flex-end;
+      }
+
       #search-input {
         -webkit-padding-end: 20px;
       }
 
+      #searching-spinner {
+        height: 20px;
+        width: 20px;
+        -webkit-padding-end: 10px;
+      }
+
       #overlay-buttons {
         margin: 0 auto;
         max-width: var(--card-max-width);
         padding: 0 var(--card-padding-side);
       }
 
       :host([has-sidebar]) #overlay-wrapper {
         -webkit-margin-start: var(--side-bar-width);
       }
 
@@ skipping 18 matching lines @@
         <div id="left-content">
           <h1 id="title">$i18n{title}</h1>
         </div>
         <div id="centered-buttons">
           <paper-button on-tap="onClearBrowsingDataTap_"
               id="clear-browsing-data-button">
             $i18n{clearBrowsingData}
           </paper-button>
         </div>
         <div id="right-content">
+          <paper-spinner id="searching-spinner" active="[[searching]]">
+          </paper-spinner>
           <cr-search-field id="search-input" label="$i18n{search}"
               clear-label="$i18n{clearSearch}">
           </cr-search-field>
         </div>
       </div>
 
       <div id="overlay-wrapper" hidden$="[[!itemsSelected_]]">
         <div id="overlay-buttons">
           <paper-icon-button icon="clear" id="cancel-icon-button"
               on-tap="onClearSelectionTap_"></paper-icon-button>
           <div id="number-selected">[[numberOfItemsSelected_(count)]]</div>
           <paper-button id="cancel-button" on-tap="onClearSelectionTap_">
             $i18n{cancel}
           </paper-button>
           <paper-button id="delete-button" on-tap="onDeleteTap_">
             $i18n{delete}
           </paper-button>
         </div>
       </div>
     </div>
   </template>
   <script src="chrome://history/history_toolbar.js"></script>
 </dom-module>