Perf metric tracking the wallclock time it takes to show a new tab page.

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 d1800f8261a89d2e3f42ae6331697e1debe91683..95d8c0b218fbcfee82be211f084b8d564ef1ac6c 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -75587,6 +75587,24 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Toolbar.Menu.NewIncognitoTabPresentationDuration" units="ms">
+  <owner>peterlaurens@chromium.org</owner>
+  <summary>
+    The number of millseconds between the user requesting a new incognito tab,
+    e.g. by tapping the New Incognito Tab entry in the main tools menu, and it
+    completing its animation on screen.
+  </summary>
+</histogram>
+
+<histogram name="Toolbar.Menu.NewTabPresentationDuration" units="ms">
+  <owner>peterlaurens@chromium.org</owner>
+  <summary>
+    The number of millseconds between the user requesting a new tab, e.g. by
+    tapping the New Tab entry in the main tools menu, and it completing its
+    animation on screen.
+  </summary>
+</histogram>
+
 <histogram name="TopSites.NumberOfApplyBlacklist">
   <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
   <summary>The number of times TopSitesImpl::ApplyBlacklist is called.</summary>