UKM: Added support for navigation sources

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 1c4d44452cc5eedec98d0cd66ee04273ec5dda27..c3cd3ac006c3e1231dc271fecb4c27fd57923753 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -70290,6 +70290,21 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <summary>The status when loading UKM PersistedLogs from Prefs.</summary>
 </histogram>
 
+<histogram name="UKM.Sources.MaxSourcesHit" units="BooleanHit">
+  <owner>holte@chromium.org</owner>
+  <owner>rkaplow@chromium.org</owner>
+  <summary>
+    Counter for the number of times an UKM source was discarded due to the max
+    in-memory limit being hit.
+  </summary>
+</histogram>
+
+<histogram name="UKM.Sources.SerializedCount">
+  <owner>holte@chromium.org</owner>
+  <owner>rkaplow@chromium.org</owner>
+  <summary>Counter for number of serialized UKM sources.</summary>

[rkaplow, 2017/01/25 21:30:06]

when storing a UKM log.

[oystein (OOO til 10th of July), 2017/01/28 00:02:20]

Done.

+</histogram>
+
 <histogram name="UKM.UnsentLogs.DroppedSize" units="bytes">
   <owner>holte@chromium.org</owner>
   <owner>rkaplow@chromium.org</owner>