arc: Provide UMA for OptIn flow.

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 2594ab1e291b8407e67f72300b03cf6b45865397..8d66a465fb9bf2c9f3e788414289727ecaf0bc90 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -1540,6 +1540,12 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <summary>Arc OptIn cancelation reason.</summary>
 </histogram>
 
+<histogram name="Arc.OptInResult" enum="ArcOptInResult">
+  <owner>elijahtaylor@google.com</owner>
+  <owner>khmel@google.com</owner>
+  <summary>Arc OptIn flow result.</summary>
+</histogram>
+
 <histogram name="Arc.OptInSilentAuthCode" enum="ArcOptInSilentAuthCode">
   <owner>elijahtaylor@google.com</owner>
   <summary>
@@ -81937,11 +81943,25 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="0" label="Canceled by user"/>
   <int value="1" label="Unclassified failure"/>
   <int value="2" label="Network failure"/>
-  <int value="3" label="GMS Services are not available"/>
+  <int value="3" label="DEPRECATED: GMS Services are not available"/>
   <int value="4" label="DEPRECATED: Bad authentication returned by server"/>
   <int value="5" label="DEPRECATED: GMS Core is not available"/>
   <int value="6" label="Cloud provision flow failed"/>
   <int value="7" label="Android Management required"/>
+  <int value="8" label="Busy"/>
+</enum>
+
+<enum name="ArcOptInResult" type="int">
+  <summary>
+    Defines Arc OptIn flow states. Normally each OptIn flow reports 2-3 states;
+    Started should be accompined with Succeeded or Canceled. Optionally
+    Succeeded after retry or Canceled after error may be provided.
+  </summary>
+  <int value="0" label="Started"/>
+  <int value="1" label="Succeeded"/>
+  <int value="2" label="Succeeded after retry"/>
+  <int value="3" label="Canceled"/>
+  <int value="4" label="Canceled after error"/>
 </enum>
 
 <enum name="ArcOptInSilentAuthCode" type="int">