MD History: Refresh the list when clearing browsing data

chrome/browser/resources/md_history/history_list.js

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 Polymer({
   is: 'history-list',
 
   properties: {
     // The search term for the current query. Set when the query returns.
     searchedTerm: {
@@ skipping 63 matching lines @@
 
     if (this.lastSearchedTerm_ != this.searchedTerm) {
       this.resultLoadingDisabled_ = false;
       if (this.historyData_)
         this.splice('historyData_', 0, this.historyData_.length);
       this.fire('unselect-all');
       this.lastSearchedTerm_ = this.searchedTerm;
     }
 
     if (this.historyData_) {
-      // If we have previously received data, push the new items onto the
-      // existing array.
-      results.unshift('historyData_');
-      this.push.apply(this, results);

[lshang, 2016/08/04 00:17:04]

These two lines seem not right.

When there are new items coming and the list is refreshed automatically, the
fetched 'results' will include all updated history items including new items and
old items, and 'unshift' method will append 'results' to historyData_, which
will result in historyData_ having 2 copies of old items?

It hasn't caused any problems, which I think is because we now don't support
refreshing history list automatically when user navigates to new websites, so
that these code only get executed when search term changes, which will clear
historyData_ ahead on line 78.

Please correct me if I understand it wrong:-)

[tsergeant, 2016/08/04 01:25:55]

These lines support infinite scrolling. When we do an incremental query, we
receive new data which gets appended directly after the old data.

You'll need to keep this logic in place while adding in separate logic for
refreshing the list.

[lshang, 2016/08/05 03:39:03]

Ah, it's for infinite scrolling! Then it makes sense now. I've added them back.

+      // If we have previously received data, refresh the list unless the user
+      // has any items checked.
+      var selectedItem = this.historyData_.filter(function(item) {
+        return item.selected;
+      });
+      if (selectedItem.length == 0) {
+        this.splice('historyData_', 0, this.historyData_.length);
+        this.set('historyData_', results);
+      }
     } else {
       // The first time we receive data, use set() to ensure the iron-list is
       // initialized correctly.
       this.set('historyData_', results);
     }
   },
 
   /**
    * Cycle through each entry in historyData_ and set all items to be
    * unselected.
@@ skipping 140 matching lines @@
     return index == 0;
   },
 
   /**
    * @private
    */
   notifyListScroll_: function() {
     this.fire('history-list-scrolled');
   },
 });