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

chrome/browser/resources/md_history/history_toolbar.html

Index: chrome/browser/resources/md_history/history_toolbar.html
diff --git a/chrome/browser/resources/md_history/history_toolbar.html b/chrome/browser/resources/md_history/history_toolbar.html
index ea78ae2531d49b86025bd9ea70aeff915afe15de..f081938c47dc3f0ab530d547d04e73894bba0b90 100644
--- a/chrome/browser/resources/md_history/history_toolbar.html
+++ b/chrome/browser/resources/md_history/history_toolbar.html
@@ -41,6 +41,15 @@
         -webkit-padding-end: 20px;
       }
 
+      #searching-spinner {
+        top: 15px;

[tsergeant, 2016/04/15 05:14:50]

Is this necessary?

[lshang, 2016/04/18 00:29:00]

Done.

+      }
+
+      paper-spinner.search {
+        height: 20px;
+        width: 20px;
+      }
+
       #items {
         margin: 0 auto;
         max-width: var(--card-max-width);
@@ -85,6 +94,10 @@
     <div id="toolbar-container">
       <div id="main-content" hidden$="[[itemsSelected_]]">
         <h1 id="title">$i18n{title}</h1>
+        <div id="searching-spinner"  hidden$="[[!searching_]]">
+          <paper-spinner class="search" alt="searching in history" active>

[tsergeant, 2016/04/15 05:14:50]

Same comment here about localization.

However, since the alt-text is only used by screen readers, depending on how the
screen reader works, it might not be necessary to set the alt-text on both
spinners -- it might work fine if you leave one empty.

[lshang, 2016/04/18 00:29:00]

Done.

+          </paper-spinner>
+        </div>
         <cr-search-field id="search-input" label="$i18n{search}"
             clear-label="$i18n{clearSearch}">
         </cr-search-field>