Handles unknown signin status and collect more stats.

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 5f6cffbc3a81186f5c6da1a79d3230a4b40e6fcb..8768471982968e0b5c100569c29a0e4c36f0ed60 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -38744,7 +38744,10 @@ Therefore, the affected-histogram name has to have at least one dot in it.
 
 <enum name="ComputeCurrentSigninStatus" type="int">
   <int value="0" label="Tried to compute current signin status."/>
-  <int value="1" label="No signin manager found."/>
+  <int value="1" label="Error: No profiles found."/>
+  <int value="2" label="No opened browser found."/>
+  <int value="3" label="User signed in when the signin status is unknown."/>
+  <int value="4" label="User signed out when the signin status is unknown."/>
 </enum>
 
 <enum name="ConnectionFailureReason" type="int">
@@ -48401,6 +48404,7 @@ To add a new entry, add it with any value and run test to compute valid value.
   <int value="1" label="All profiles not signed in"/>
   <int value="2" label="Mixed signin status"/>
   <int value="3" label="Unknown signin status"/>
+  <int value="4" label="Error getting signin status"/>
 </enum>
 
 <enum name="ProfileSync" type="int">