Add enum description for license fetch failure.

This is a follow-up for CL 2959853003 that added a new enum value.

Bug: None
Change-Id: I528b0078ec036630f7747c4a4f85bfcd6d2a3158
Reviewed-on: https://chromium-review.googlesource.com/c/1296251Reviewed-by: Sergey Poromov <poromov@chromium.org>
Commit-Queue: Sergey Poromov <poromov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#601915}

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

@@ -12,6 +12,9 @@ namespace policy {
 
 // Metrics collected for enterprise events.
 
+// When you add new values do not forget to update
+// tools/metrics/histograms/enums.xml
+
 // 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.

tools/metrics/histograms/enums.xml

@@ -14204,6 +14204,9 @@ Called by update_net_error_codes.py.-->
   <int value="56" label="Store DM token failed">
     Failed to store DM token into the local state.
   </int>
+  <int value="57" label="License list fetch failed">
+    Failed to get available licenses from server.
+  </int>
 </enum>
 
 <enum name="EnterpriseExistingInstallAttributesLockType">