Push API: Refactor and fix unsubscribe API

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 9dd87ebcc54f3519296897a111ec1a20a81ed6bb..33c59d57a37bf98c49f522b468b1b6d5167bf8b2 100644
--- a/content/public/common/push_messaging_status.h
+++ b/content/public/common/push_messaging_status.h
@@ -65,6 +65,35 @@ enum PushRegistrationStatus {
       PUSH_REGISTRATION_STATUS_MANIFEST_EMPTY_OR_MISSING
 };
 
+// Push unregistration reason for reporting in UMA.

[Mark P, 2016/09/30 22:39:03]

Please add standard warning label here (yes, I see you have something similar
below too), something like
These values are written to logs.  New enum values can be added, but existing
enums must never be renumbered or deleted and reused.

[johnme, 2016/09/30 23:10:41]

Done (added "Enum values can be added, but must never be renumbered or deleted
and reused." to each of the enums in this class, as they're all used for UMA).

+enum PushUnregistrationReason {
+  // Should never happen.
+  PUSH_UNREGISTRATION_REASON_UNKNOWN = 0,
+
+  // Unregistering because the website called the unsubscribe API.
+  PUSH_UNREGISTRATION_REASON_JAVASCRIPT_API = 1,
+
+  // Unregistering because the user manually revoked permission.
+  PUSH_UNREGISTRATION_REASON_PERMISSION_REVOKED = 2,
+
+  // Automatic - incoming message's app id was unknown.
+  PUSH_UNREGISTRATION_REASON_DELIVERY_UNKNOWN_APP_ID = 3,
+
+  // Automatic - incoming message's origin no longer has permission.
+  PUSH_UNREGISTRATION_REASON_DELIVERY_PERMISSION_DENIED = 4,
+
+  // Automatic - incoming message's service worker was not found.
+  PUSH_UNREGISTRATION_REASON_DELIVERY_NO_SERVICE_WORKER = 5,
+
+  // 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_UNREGISTRATION_REASON_LAST below.
+
+  PUSH_UNREGISTRATION_REASON_LAST =
+      PUSH_UNREGISTRATION_REASON_DELIVERY_NO_SERVICE_WORKER
+};
+
 // Push unregistration success/error codes for internal use & reporting in UMA.
 enum PushUnregistrationStatus {
   // The unregistration was successful.