Disallow repeated PushManager.subscribes with different sender ids

content/public/common/push_messaging_status.h

Index: content/public/common/push_messaging_status.h
diff --git a/content/public/common/push_messaging_status.h b/content/public/common/push_messaging_status.h
index 8b9fb0a32ba79750e4a296e6fd62960e9bc159d7..d8d7e7e1089724eefc0466b900dfb25fa696f3b0 100644
--- a/content/public/common/push_messaging_status.h
+++ b/content/public/common/push_messaging_status.h
@@ -57,13 +57,16 @@ enum PushRegistrationStatus {
   // empty.
   PUSH_REGISTRATION_STATUS_MANIFEST_EMPTY_OR_MISSING = 12,
 
+  // Registration failed because a subscription with a different sender id
+  // already exists.
+  PUSH_REGISTRATION_STATUS_SENDER_ID_MISMATCH = 13,
+
   // NOTE: Do not renumber these as that would confuse interpretation of
   // previously logged data. When making changes, also update the enum list
   // in tools/metrics/histograms/histograms.xml to keep it in sync, and
   // update PUSH_REGISTRATION_STATUS_LAST below.
 
-  PUSH_REGISTRATION_STATUS_LAST =
-      PUSH_REGISTRATION_STATUS_MANIFEST_EMPTY_OR_MISSING
+  PUSH_REGISTRATION_STATUS_LAST = PUSH_REGISTRATION_STATUS_SENDER_ID_MISMATCH
 };
 
 // Push unregistration reason for reporting in UMA. Enum values can be added,