Log the ratio of the duration spent adding the two JumpList categories

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index df5dbbca25f4e8a4e22639aef070f7db1411c1b4..56762965024429d0047a879ef92260a24a5fad59 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -22133,7 +22133,8 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <summary>Records the source that requested showing the feedback app.</summary>
 </histogram>
 
-<histogram name="FileBrowser.ChangeDirectory.RootType" enum="FileManagerRootType">
+<histogram name="FileBrowser.ChangeDirectory.RootType"
+    enum="FileManagerRootType">
   <owner>yamaguchi@chromium.com</owner>
   <summary>
     Chrome OS File Browser: Counts the number of directory-changed events,
@@ -87396,6 +87397,14 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <summary>Time spent in OnFaviconDataAvailable().</summary>
 </histogram>
 
+<histogram name="WinJumplist.RatioAddCategoryTime" units="scaled ratio">
+  <owner>chengx@chromium.org</owner>
+  <summary>
+    The ratio of the duration spent adding the most-visited category compared to
+    the duration spent adding the recently-closed category, multiplied by 10.
+  </summary>
+</histogram>
+
 <histogram name="WinJumplist.StartLoadingFaviconDuration" units="ms">
   <obsolete>
     Obsolete 06/22/2017 as it's no longer needed.