Add Bookmarks.BookmarksInFolder histogram to bookmark manager.

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

 // Copyright (c) 2012 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.
 
 // TODO(arv): Now that this is driven by a data model, implement a data model
 //            that handles the loading and the events from the bookmark backend.
 
 /**
  * @typedef {{childIds: Array<string>}}
  *
@@ skipping 131 matching lines @@
         // Failed to load bookmarks. Most likely due to the bookmark being
         // removed.
         cr.dispatchSimpleEvent(this, 'invalidId');
         return;
       }
 
       this.dataModel = new BookmarksArrayDataModel(items);
 
       this.fixWidth_();
       cr.dispatchSimpleEvent(this, 'load');
+      chrome.metricsPrivate.recordValue({
+        'metricName': 'Bookmarks.BookmarksInFolder',
+        'type': chrome.metricsPrivate.MetricTypeType.HISTOGRAM_LOG,
+        'min': 0,
+        'max': 200,

[Dan Beam, 2016/11/16 01:26:51]

wait, why a max of 200?

[Alexei Svitkine (slow), 2016/11/16 01:34:09]

Suggest using equivalent of UMA_HISTOGRAM_COUNTS_1000().

That is, min:1, max:1000, buckets:50

You can also mention that macro in the comment above.

(Note: The min:1 will still give you a 0-1 bucket since there's always a 0
bucket.)

[calamity, 2016/11/16 01:57:46]

Done.

+        'buckets': 10
+      }, this.dataModel.length);
+      console.log(this.dataModel.length);

[Dan Beam, 2016/11/16 01:26:51]

nit: remove the log()

[calamity, 2016/11/16 01:57:46]

Done.

     },
 
     /**
      * The bookmark node that the list is currently displaying. If we are
      * currently displaying search this returns null.
      * @type {BookmarkTreeNode}
      */
     get bookmarkNode() {
       if (this.isSearch())
         return null;
@@ skipping 478 matching lines @@
         }
       }
     }
   };
 
   return {
     BookmarkList: BookmarkList,
     list: /** @type {Element} */(null),  // Set when decorated.
   };
 });