Add Bookmarks.BookmarksInFolder histogram to bookmark manager.

chrome/browser/resources/bookmark_manager/js/bmm/bookmark_list.js

Index: chrome/browser/resources/bookmark_manager/js/bmm/bookmark_list.js
diff --git a/chrome/browser/resources/bookmark_manager/js/bmm/bookmark_list.js b/chrome/browser/resources/bookmark_manager/js/bmm/bookmark_list.js
index 4914b68e8c26e355cd7f83febb7473aebaccd6e4..87be223908241ddbf0e71266d25e2616434a0eb4 100644
--- a/chrome/browser/resources/bookmark_manager/js/bmm/bookmark_list.js
+++ b/chrome/browser/resources/bookmark_manager/js/bmm/bookmark_list.js
@@ -149,6 +149,14 @@ cr.define('bmm', function() {
 
       this.fixWidth_();
       cr.dispatchSimpleEvent(this, 'load');
+      chrome.metricsPrivate.recordValue({
+        'metricName': 'Bookmarks.BookmarksInFolder',
+        'type': chrome.metricsPrivate.MetricTypeType.HISTOGRAM_LOG,
+        'min': 0,
+        'max': 200,
+        'buckets': 10

[Alexei Svitkine (slow), 2016/11/16 00:45:30]

Are you sure 10 buckets is sufficient?

[calamity, 2016/11/16 00:52:27]

For our purposes, probably, but I guess more would me more future-proof? Any
recommendations?

Our intent is to gauge the scale of items in folders so we can understand the
performance of the new bookmark manager UI with real world data loads.

+      }, this.dataModel.length);
+      console.log(this.dataModel.length);
     },
 
     /**