[Sync] Record histogram for mismatched device_ids

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 2e0e9c78b527cdec7d535768401871584e5365ab..76dd37645be984dd61185c2616847f0de2a5f857 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -40280,6 +40280,15 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="Sync.DeviceIdMismatchDetails" enum="DeviceIdMismatch">
+  <owner>pavely@chromium.org</owner>
+  <summary>
+    When signin_scoped_device_id from pref doesn't match the one in
+    DeviceInfoSpecfics this histogram tells if sync or pref copy was empty. This
+    will indicate how often such mismatch happens and what was the state before.
+  </summary>
+</histogram>
+
 <histogram name="Sync.DictionaryAssociationTime" units="milliseconds">
   <owner>zea@chromium.org</owner>
   <summary>Time taken during dictionary association.</summary>
@@ -48389,6 +48398,12 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   <int value="5" label="First window capture call failed."/>
 </enum>
 
+<enum name="DeviceIdMismatch" type="int">
+  <int value="0" label="BOTH_NONEMPTY"/>
+  <int value="1" label="SYNC_EMPTY"/>
+  <int value="2" label="PREF_EMPTY"/>
+</enum>
+
 <enum name="DeviceOrientationSensorTypeAndroid" type="int">
   <int value="0" label="Not Available"/>
   <int value="1" label="ROTATION_VECTOR"/>