[MD History] Copy stats from the old history page.

chrome/browser/resources/md_history/history_list_behavior.js

Index: chrome/browser/resources/md_history/history_list_behavior.js
diff --git a/chrome/browser/resources/md_history/history_list_behavior.js b/chrome/browser/resources/md_history/history_list_behavior.js
index 230139f0f6593d0a306ad753f864088a55f16d7a..511c76d68faca7e7a7ba0bb8db2805a986506237 100644
--- a/chrome/browser/resources/md_history/history_list_behavior.js
+++ b/chrome/browser/resources/md_history/history_list_behavior.js
@@ -94,6 +94,7 @@ var HistoryListBehavior = {
         .then(function() {
           this.removeItemsByPath(Array.from(this.selectedPaths));
           this.fire('unselect-all');
+          this.refreshItemIndexes();
         }.bind(this));
   },
 
@@ -164,7 +165,7 @@ var HistoryListBehavior = {
     node.indexes.sort(function(a, b) { return b - a; });
     node.indexes.forEach(function(index) {
       if (node.leaf || this.removeItemsBeneathNode_(node.children[index])) {
-        var item = array.splice(index, 1);
+        var item = array.splice(index, 1)[0];
         splices.push({
           index: index,
           removed: [item],
@@ -172,6 +173,19 @@ var HistoryListBehavior = {
           object: array,
           type: 'splice'
         });
+
+        if (item.index == undefined)
+          return;
+
+        var browserService = md_history.BrowserService.getInstance();
+        browserService.recordHistogram(
+            'HistoryPage.RemoveEntryPosition', item.index,
+            UMA_MAX_BUCKET_VALUE);
+        if (item.index <= UMA_MAX_SUBSET_BUCKET_VALUE) {
+          browserService.recordHistogram(
+              'HistoryPage.RemoveEntryPositionSubset', item.index,
+              UMA_MAX_SUBSET_BUCKET_VALUE);
+        }
       }
     }.bind(this));