Fix EnterpriseDeviceManagementStatus UMA enum, add comments.

components/policy/core/common/cloud/enterprise_metrics.h

Index: components/policy/core/common/cloud/enterprise_metrics.h
diff --git a/components/policy/core/common/cloud/enterprise_metrics.h b/components/policy/core/common/cloud/enterprise_metrics.h
index 79bdcf168501165e28d78e749a409d8ba68dee82..9ea3cf4abb14f8be65ee8c2edba92e973c81cdc0 100644
--- a/components/policy/core/common/cloud/enterprise_metrics.h
+++ b/components/policy/core/common/cloud/enterprise_metrics.h
@@ -13,199 +13,219 @@ namespace policy {
 
 // Events related to fetching, saving and loading DM server tokens.
 // These metrics are collected both for device and user tokens.
+// This enum is used to define the buckets for an enumerated UMA histogram.
+// Hence,
+//   (a) existing enumerated constants should never be deleted or reordered, and
+//   (b) new constants should only be appended at the end of the enumeration.
 enum MetricToken {
   // A cached token was successfully loaded from disk.
-  kMetricTokenLoadSucceeded,
+  kMetricTokenLoadSucceeded = 0,
   // Reading a cached token from disk failed.
-  kMetricTokenLoadFailed,
+  kMetricTokenLoadFailed = 1,
 
   // A token fetch request was sent to the DM server.
-  kMetricTokenFetchRequested,
+  kMetricTokenFetchRequested = 2,
   // The request was invalid, or the HTTP request failed.
-  kMetricTokenFetchRequestFailed,
+  kMetricTokenFetchRequestFailed = 3,
   // Error HTTP status received, or the DM server failed in another way.
-  kMetricTokenFetchServerFailed,
+  kMetricTokenFetchServerFailed = 4,
   // A response to the fetch request was received.
-  kMetricTokenFetchResponseReceived,
+  kMetricTokenFetchResponseReceived = 5,
   // The response received was invalid. This happens when some expected data
   // was not present in the response.
-  kMetricTokenFetchBadResponse,
+  kMetricTokenFetchBadResponse = 6,
   // DM server reported that management is not supported.
-  kMetricTokenFetchManagementNotSupported,
+  kMetricTokenFetchManagementNotSupported = 7,
   // DM server reported that the given device ID was not found.
-  kMetricTokenFetchDeviceNotFound,
+  kMetricTokenFetchDeviceNotFound = 8,
   // DM token successfully retrieved.
-  kMetricTokenFetchOK,
+  kMetricTokenFetchOK = 9,
 
   // Successfully cached a token to disk.
-  kMetricTokenStoreSucceeded,
+  kMetricTokenStoreSucceeded = 10,
   // Caching a token to disk failed.
-  kMetricTokenStoreFailed,
+  kMetricTokenStoreFailed = 11,
 
   // DM server reported that the device-id generated is not unique.
-  kMetricTokenFetchDeviceIdConflict,
+  kMetricTokenFetchDeviceIdConflict = 12,
   // DM server reported that the serial number we try to register is invalid.
-  kMetricTokenFetchInvalidSerialNumber,
+  kMetricTokenFetchInvalidSerialNumber = 13,
   // DM server reported that the licenses for the domain have expired or been
   // exhausted.
-  kMetricMissingLicenses,
+  kMetricMissingLicenses = 14,
 
   kMetricTokenSize  // Must be the last.
 };
 
 // Events related to fetching, saving and loading user and device policies.
+// This enum is used to define the buckets for an enumerated UMA histogram.
+// Hence,
+//   (a) existing enumerated constants should never be deleted or reordered, and
+//   (b) new constants should only be appended at the end of the enumeration.
 enum MetricPolicy {
   // A cached policy was successfully loaded from disk.
-  kMetricPolicyLoadSucceeded,
+  kMetricPolicyLoadSucceeded = 0,
   // Reading a cached policy from disk failed.
-  kMetricPolicyLoadFailed,
+  kMetricPolicyLoadFailed = 1,
 
   // A policy fetch request was sent to the DM server.
-  kMetricPolicyFetchRequested,
+  kMetricPolicyFetchRequested = 2,
   // The request was invalid, or the HTTP request failed.
-  kMetricPolicyFetchRequestFailed,
+  kMetricPolicyFetchRequestFailed = 3,
   // Error HTTP status received, or the DM server failed in another way.
-  kMetricPolicyFetchServerFailed,
+  kMetricPolicyFetchServerFailed = 4,
   // Policy not found for the given user or device.
-  kMetricPolicyFetchNotFound,
+  kMetricPolicyFetchNotFound = 5,
   // DM server didn't accept the token used in the request.
-  kMetricPolicyFetchInvalidToken,
+  kMetricPolicyFetchInvalidToken = 6,
   // A response to the policy fetch request was received.
-  kMetricPolicyFetchResponseReceived,
+  kMetricPolicyFetchResponseReceived = 7,
   // The policy response message didn't contain a policy, or other data was
   // missing.
-  kMetricPolicyFetchBadResponse,
+  kMetricPolicyFetchBadResponse = 8,
   // Failed to decode the policy.
-  kMetricPolicyFetchInvalidPolicy,
+  kMetricPolicyFetchInvalidPolicy = 9,
   // The device policy was rejected because its signature was invalid.
-  kMetricPolicyFetchBadSignature,
+  kMetricPolicyFetchBadSignature = 10,
   // Rejected policy because its timestamp is in the future.
-  kMetricPolicyFetchTimestampInFuture,
+  kMetricPolicyFetchTimestampInFuture = 11,
   // Device policy rejected because the device is not managed.
-  kMetricPolicyFetchNonEnterpriseDevice,
+  kMetricPolicyFetchNonEnterpriseDevice = 12,
   // The policy was provided for a username that is different from the device
   // owner, and the policy was rejected.
-  kMetricPolicyFetchUserMismatch,
+  kMetricPolicyFetchUserMismatch = 13,
   // The policy was rejected for another reason. Currently this can happen
   // only for device policies, when the SignedSettings fail to store or retrieve
   // a stored policy.
-  kMetricPolicyFetchOtherFailed,
+  kMetricPolicyFetchOtherFailed = 14,
   // The fetched policy was accepted.
-  kMetricPolicyFetchOK,
+  kMetricPolicyFetchOK = 15,
   // The policy just fetched didn't have any changes compared to the cached
   // policy.
-  kMetricPolicyFetchNotModified,
+  kMetricPolicyFetchNotModified = 16,
 
   // Successfully cached a policy to disk.
-  kMetricPolicyStoreSucceeded,
+  kMetricPolicyStoreSucceeded = 17,
   // Caching a policy to disk failed.
-  kMetricPolicyStoreFailed,
+  kMetricPolicyStoreFailed = 18,
 
   kMetricPolicySize  // Must be the last.
 };
 
 // Events related to device enrollment.
+// This enum is used to define the buckets for an enumerated UMA histogram.
+// Hence,
+//   (a) existing enumerated constants should never be deleted or reordered, and
+//   (b) new constants should only be appended at the end of the enumeration.
 enum MetricEnrollment {
   // The enrollment screen was closed without completing the enrollment
   // process.
-  kMetricEnrollmentCancelled,
+  kMetricEnrollmentCancelled = 0,
   // The user submitted credentials and started the enrollment process.
-  kMetricEnrollmentStarted,
+  kMetricEnrollmentStarted = 1,
   // Enrollment failed due to a network error.
-  kMetricEnrollmentNetworkFailed,
+  kMetricEnrollmentNetworkFailed = 2,
   // Enrollment failed because logging in to Gaia failed.
-  kMetricEnrollmentLoginFailed,
+  kMetricEnrollmentLoginFailed = 3,
   // Enrollment failed because it is not supported for the account used.
-  kMetricEnrollmentNotSupported,
+  kMetricEnrollmentNotSupported = 4,
   // Enrollment failed because it failed to apply device policy.
-  kMetricEnrollmentPolicyFailed,
+  kMetricEnrollmentPolicyFailed = 5,
   // Enrollment failed due to an unexpected error. This currently happens when
   // the Gaia auth token is not issued for the DM service, the device cloud
   // policy subsystem isn't initialized, or when fetching Gaia tokens fails
   // for an unknown reason.
-  kMetricEnrollmentOtherFailed,
+  kMetricEnrollmentOtherFailed = 6,
   // Enrollment was successful.
-  kMetricEnrollmentOK,
+  kMetricEnrollmentOK = 7,
   // Enrollment failed because the serial number we try to register is not
   // assigned to the domain used.
-  kMetricEnrollmentInvalidSerialNumber,
+  kMetricEnrollmentInvalidSerialNumber = 8,
   // Auto-enrollment started automatically after the user signed in.
-  kMetricEnrollmentAutoStarted,
+  kMetricEnrollmentAutoStarted = 9,
   // Auto-enrollment failed.
-  kMetricEnrollmentAutoFailed,
+  kMetricEnrollmentAutoFailed = 10,
   // Auto-enrollment was retried after having failed before.
-  kMetricEnrollmentAutoRetried,
+  kMetricEnrollmentAutoRetried = 11,
   // Auto-enrollment was canceled through the opt-out dialog.
-  kMetricEnrollmentAutoCancelled,
+  kMetricEnrollmentAutoCancelled = 12,
   // Auto-enrollment succeeded.
-  kMetricEnrollmentAutoOK,
+  kMetricEnrollmentAutoOK = 13,
   // Enrollment failed because the enrollment mode was not supplied by the
   // DMServer or the mode is not known to the client.
-  kMetricEnrollmentInvalidEnrollmentMode,
+  kMetricEnrollmentInvalidEnrollmentMode = 14,
   // Auto-enrollment is not supported for the mode supplied by the server.
   // This presently means trying to auto-enroll in kiosk mode.
-  kMetricEnrollmentAutoEnrollmentNotSupported,
+  kMetricEnrollmentAutoEnrollmentNotSupported = 15,
   // The lockbox initialization has taken too long to complete and the
   // enrollment has been canceled because of that.
-  kMetricLockboxTimeoutError,
+  kMetricLockboxTimeoutError = 16,
   // The username used to re-enroll the device does not belong to the domain
   // that the device was initially enrolled to.
-  kMetricEnrollmentWrongUserError,
+  kMetricEnrollmentWrongUserError = 17,
   // DM server reported that the licenses for the domain has expired or been
   // exhausted.
-  kMetricMissingLicensesError,
+  kMetricMissingLicensesError = 18,
   // Enrollment failed because the robot account auth code couldn't be
   // fetched from the DM Server.
-  kMetricEnrollmentRobotAuthCodeFetchFailed,
+  kMetricEnrollmentRobotAuthCodeFetchFailed = 19,
   // Enrollment failed because the robot account auth code couldn't be
   // exchanged for a refresh token.
-  kMetricEnrollmentRobotRefreshTokenFetchFailed,
+  kMetricEnrollmentRobotRefreshTokenFetchFailed = 20,
   // Enrollment failed because the robot account refresh token couldn't be
   // persisted on the device.
-  kMetricEnrollmentRobotRefreshTokenStoreFailed,
+  kMetricEnrollmentRobotRefreshTokenStoreFailed = 21,
   // Enrollment failed because the administrator has deprovisioned the device.
-  kMetricEnrollmentDeprovisioned,
+  kMetricEnrollmentDeprovisioned = 22,
   // Enrollment failed because the device doesn't belong to the domain.
-  kMetricEnrollmentDomainMismatch,
+  kMetricEnrollmentDomainMismatch = 23,
   // Enrollment has been triggered, the credential screen has been shown.
-  kMetricEnrollmentTriggered,
+  kMetricEnrollmentTriggered = 24,
   // The user retried to submitted credentials.
-  kMetricEnrollmentRetried,
+  kMetricEnrollmentRetried = 25,
 
   kMetricEnrollmentSize  // Must be the last.
 };
 
 // Events related to policy refresh.
+// This enum is used to define the buckets for an enumerated UMA histogram.
+// Hence,
+//   (a) existing enumerated constants should never be deleted or reordered, and
+//   (b) new constants should only be appended at the end of the enumeration.
 enum MetricPolicyRefresh {
   // A refresh occurred while the policy was not invalidated and the policy was
   // changed. Invalidations were enabled.
-  METRIC_POLICY_REFRESH_CHANGED,
+  METRIC_POLICY_REFRESH_CHANGED = 0,
   // A refresh occurred while the policy was not invalidated and the policy was
   // changed. Invalidations were disabled.
-  METRIC_POLICY_REFRESH_CHANGED_NO_INVALIDATIONS,
+  METRIC_POLICY_REFRESH_CHANGED_NO_INVALIDATIONS = 1,
   // A refresh occurred while the policy was not invalidated and the policy was
   // unchanged.
-  METRIC_POLICY_REFRESH_UNCHANGED,
+  METRIC_POLICY_REFRESH_UNCHANGED = 2,
   // A refresh occurred while the policy was invalidated and the policy was
   // changed.
-  METRIC_POLICY_REFRESH_INVALIDATED_CHANGED,
+  METRIC_POLICY_REFRESH_INVALIDATED_CHANGED = 3,
   // A refresh occurred while the policy was invalidated and the policy was
   // unchanged.
-  METRIC_POLICY_REFRESH_INVALIDATED_UNCHANGED,
+  METRIC_POLICY_REFRESH_INVALIDATED_UNCHANGED = 4,
 
   METRIC_POLICY_REFRESH_SIZE  // Must be the last.
 };
 
 // Types of policy invalidations.
+// This enum is used to define the buckets for an enumerated UMA histogram.
+// Hence,
+//   (a) existing enumerated constants should never be deleted or reordered, and
+//   (b) new constants should only be appended at the end of the enumeration.
 enum PolicyInvalidationType {
   // The invalidation contained no payload.
-  POLICY_INVALIDATION_TYPE_NO_PAYLOAD,
+  POLICY_INVALIDATION_TYPE_NO_PAYLOAD = 0,
   // A normal invalidation containing a payload.
-  POLICY_INVALIDATION_TYPE_NORMAL,
+  POLICY_INVALIDATION_TYPE_NORMAL = 1,
   // The invalidation contained no payload and was considered expired.
-  POLICY_INVALIDATION_TYPE_NO_PAYLOAD_EXPIRED,
+  POLICY_INVALIDATION_TYPE_NO_PAYLOAD_EXPIRED = 3,
   // The invalidation contained a payload and was considered expired.
-  POLICY_INVALIDATION_TYPE_EXPIRED,
+  POLICY_INVALIDATION_TYPE_EXPIRED = 4,
 
   POLICY_INVALIDATION_TYPE_SIZE  // Must be the last.
 };