Report frequency of single page app navigations to UMA

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 283764be1bfafc909eb53e15c8daee43058f5cfd..f498916e0075c85302f1e328fc5ec579d8ab1a19 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -60388,6 +60388,15 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="RendererScheduler.UpdateForSameDocumentNavigationCount"
+    units="ms">

[tdresser, 2017/06/13 15:21:29]

Take a look at another histogram with an enum value. There shouldn't be any
units, and you'll need to defined an enum, which lines up with the FrameLoadType
enum.

It's annoying that there's no good way of testing these changes, other than
landing them, and then looking at the dashboard. Thankfully, the dashboard pulls
in updates out of band from Chrome updates, so if something is broken, it's
generally pretty quick to fix.

[Liquan (Max) Gu, 2017/06/20 23:35:39]

Done.

+  <owner>maxlg@chromium.org</owner>
+  <summary>
+    The number of single page app navigations per frame load type, reported each
+    time when the same document navigation is updated.
+  </summary>
+</histogram>
+
 <histogram name="RendererScheduler.UserModel.GestureDuration" units="ms">
   <owner>alexclarke@chromium.org</owner>
   <summary>Duration of gestures (scrolls and pinches).</summary>