android: Record the source of account change notifications from GSA.

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 5ff826f91882fdafd855d07aba96a376fed17b42..d052a995b1dc14f14b576c5d1cd19ca09ab6cb15 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -59122,6 +59122,16 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Search.GsaAccountChangeNotificationSource"
+    enum="GsaAccountChangeNotificationSource">
+  <owner>lizeb@chromium.org</owner>
+  <summary>
+    On Android, when GSA tells Chrome about an account change, what is the
+    notification mechanism used, which is either the service connection, or a
+    broadcast. Recorded once per account change.
+  </summary>
+</histogram>
+
 <histogram name="Search.GsaBroadcastsAccountChanges"
     enum="BooleanAccountChange">
   <owner>lizeb@chromium.org</owner>
@@ -91416,6 +91426,11 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </int>
 </enum>
 
+<enum name="GsaAccountChangeNotificationSource" type="int">
+  <int value="0" label="Service"/>
+  <int value="1" label="Broadcast"/>
+</enum>
+
 <enum name="GzipEncodingFixupResult" type="int">
   <int value="0" label="Gzip encoding left as-is"/>
   <int value="1" label="MIME type indicated GZIP content"/>