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

chrome/browser/resources/md_history/history_toolbar.js

Index: chrome/browser/resources/md_history/history_toolbar.js
diff --git a/chrome/browser/resources/md_history/history_toolbar.js b/chrome/browser/resources/md_history/history_toolbar.js
index 48189b8999f5a3216de51769244b42fd9844842c..c0a0d4d133f160f39d05f7069ae2042c7ea0de6d 100644
--- a/chrome/browser/resources/md_history/history_toolbar.js
+++ b/chrome/browser/resources/md_history/history_toolbar.js
@@ -41,6 +41,12 @@ Polymer({
     searchTerm: {
       type: String,
       value: ''
+    },
+
+    // True if it's searching at the backend.
+    searching_: {
+      type: Boolean,
+      value: false
     }
   },
 
@@ -69,6 +75,21 @@ Polymer({
   },
 
   /**
+  * Mark the toolbar as currently searching term from the back-end.

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

You can either replace these two functions with a single one:
  setSearching(value)

Or make the `searching_` property public and have history.js modify it directly:

$('toolbar').searching = true;

^ This second one has the advantage of probably not needing waitForUpgrade
anymore.

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

Done.

+  */
+  setSearching: function() {
+    this.searching_ = true;
+  },
+
+  /**
+  * Set searching as finished so that searching spinner is hidden.
+  */
+  searchingFinished: function() {
+    this.searching_ = false;
+  },
+
+
+  /**
    * If the search term has changed reload for the new search.
    */
   onSearch: function(searchTerm) {