Add UMA stats for tracking bookmark depth

chrome/browser/bookmarks/bookmark_stats.cc

 // Copyright 2013 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.
 
 #include "chrome/browser/bookmarks/bookmark_stats.h"
 
 #include "base/metrics/histogram.h"
+#include "chrome/browser/bookmarks/bookmark_model.h"
 #include "content/public/browser/user_metrics.h"
 
-void RecordBookmarkLaunch(BookmarkLaunchLocation location) {
+void RecordBookmarkLaunch(const BookmarkNode* node,
+                          BookmarkLaunchLocation location) {
   if (location == BOOKMARK_LAUNCH_LOCATION_DETACHED_BAR ||
       location == BOOKMARK_LAUNCH_LOCATION_ATTACHED_BAR) {
     content::RecordAction(
         content::UserMetricsAction("ClickedBookmarkBarURLButton"));
   }
-
   UMA_HISTOGRAM_ENUMERATION(
       "Bookmarks.LaunchLocation", location, BOOKMARK_LAUNCH_LOCATION_LIMIT);
+
+  if (!node)
+    return;
+
+  // In the cases where a bookmark node is provided, record the depth of the
+  // bookmark in the tree.
+  int depth = 0;
+  for (const BookmarkNode* iter = node; iter != NULL; iter = iter->parent()) {
+    depth++;
+  }
+  // Record |depth - 2| to offset the invisible root node and permanent nodes
+  // (Bookmark Bar, Mobile Bookmarks or Other Bookmarks)
+  UMA_HISTOGRAM_COUNTS("Bookmarks.LaunchDepth", depth - 2);
 }
 
 void RecordBookmarkFolderOpen(BookmarkLaunchLocation location) {
   if (location == BOOKMARK_LAUNCH_LOCATION_DETACHED_BAR ||
       location == BOOKMARK_LAUNCH_LOCATION_ATTACHED_BAR) {
     content::RecordAction(
         content::UserMetricsAction("ClickedBookmarkBarFolder"));
   }
 }
 
 void RecordBookmarkAppsPageOpen(BookmarkLaunchLocation location) {
   if (location == BOOKMARK_LAUNCH_LOCATION_DETACHED_BAR ||
       location == BOOKMARK_LAUNCH_LOCATION_ATTACHED_BAR) {
     content::RecordAction(
         content::UserMetricsAction("ClickedBookmarkBarAppsShortcutButton"));
   }
 }