Migrate startup URLs pref.

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 c89d3d39e449f91bb8e32cd68c1954f223dac1b5..4764ca774be995171f262a10dcc380d4eb873b0e 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -15539,6 +15539,18 @@ other types of suffix sets.
   </summary>
 </histogram>
 
+<histogram name="Settings.StartupURLsMigration" enum="StartupURLsMigration">
+  <summary>The startup URLs pref migration steps.</summary>
+</histogram>
+
+<histogram name="Settings.StartupURLsResetTime" units="milliseconds">
+  <summary>
+    The time elapsed in milliseconds in between startup URLs pref migration. A
+    value of 0 indicates that the last migration time was in the future due to
+    e.g. an incorrect system time.
+  </summary>
+</histogram>
+
 <histogram name="Settings.TrackedPreferenceChanged" enum="TrackedPreference">
   <summary>
     The id of a tracked preference whose value has been changed since the last
@@ -27240,6 +27252,12 @@ other types of suffix sets.
   <int value="15" label="PROCEED_NEW_SITE"/>
 </enum>
 
+<enum name="StartupURLsMigration" type="int">
+  <int value="0" label="Performed migration"/>
+  <int value="1" label="No migration value"/>
+  <int value="2" label="Reset migration"/>
+</enum>
+
 <enum name="SuspendStatus" type="int">
   <int value="0" label="Success"/>
   <int value="1" label="Failure"/>