Push API: Log registration success/failure codes to UMA

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 72b0586ce582bce6fc42fe9b0bf135e45b6f98c7..652c8f1faf09d52c112262ee24d43638f13ba824 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -26689,6 +26689,16 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="PushMessaging.RegistrationStatus"
+    enum="PushRegistrationStatus">
+  <owner>johnme@google.com</owner>
+  <owner>mvanouwerkerk@google.com</owner>
+  <summary>
+    When a webpage registers for push messaging, this records whether the
+    request is successful, or otherwise the type of error encountered.
+  </summary>
+</histogram>
+
 <histogram name="Quickoffice.csvFormattedCellCount">
   <owner>dskelton@google.com</owner>
   <summary>
@@ -50493,6 +50503,15 @@ To add a new entry, add it with any value and run test to compute valid value.
   <int value="22" label="DOMAIN_NUM_EVENTS"/>
 </enum>
 
+<enum name="PushRegistrationStatus" type="int">
+  <int value="0" label="Successful"/>
+  <int value="1" label="Page has no active Service Worker"/>
+  <int value="2" label="Push service not available"/>
+  <int value="3" label="Registration limit reached"/>
+  <int value="4" label="Permission denied"/>
+  <int value="5" label="Push service error"/>
+</enum>
+
 <enum name="QuicAddressMismatch" type="int">
   <int value="0" label="Address mismatch: IPv4 IPv4"/>
   <int value="1" label="Address mismatch: IPv6 IPv6"/>