[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..82d7860c5db50e2d5cb5b1a78d90cb5262db0e37 100644
--- a/chrome/browser/resources/md_history/history_list_behavior.js
+++ b/chrome/browser/resources/md_history/history_list_behavior.js
@@ -172,6 +172,14 @@ var HistoryListBehavior = {
           object: array,
           type: 'splice'
         });
+        var browserService = md_history.BrowserService.getInstance();

[tsergeant, 2016/08/18 04:14:34]

You need to be really careful about grouped history here:

1. UMA code will trigger for deleting container arrays
2. The index is relative to the container array, rather than to the overall
list.

Both of these will work fine in regular history but give wonky values in
grouped.

[calamity, 2016/08/19 13:59:44]

Oh wups, this is meant to be item.index.

Added more tests to catch all this stuff.

+        browserService.recordHistogram(
+            'HistoryPage.RemoveEntryPosition', index, UMA_MAX_BUCKET_VALUE);
+        if (index <= UMA_MAX_SUBSET_BUCKET_VALUE) {
+          browserService.recordHistogram(
+              'HistoryPage.RemoveEntryPositionSubset', index,
+              UMA_MAX_SUBSET_BUCKET_VALUE);
+        }
       }
     }.bind(this));