[Nearby] Only slice Transfer.FinalStatus metrics by one dimension

The previous implementation required slicing by send/receive, device
type, *and* contact/non-contact. These histograms were too specific to
be very useful. In this CL, we only slice by one variation.

Manually verified Nearby.Share.Transfer.FinalStatus[...] metrics.

Bug: 1105579
Change-Id: I37ed2f3113f02884ae726c86b2318575546fc880
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2619998
Commit-Queue: Josh Nohle <nohle@chromium.org>
Reviewed-by: James Vecore <vecore@google.com>
Reviewed-by: Brian White <bcwhite@chromium.org>
Cr-Commit-Position: refs/heads/master@{#842767}

chrome/browser/nearby_sharing/nearby_share_metrics_logger.cc

@@ -367,7 +367,7 @@ void RecordNearbyShareTransferFinalStatusMetric(
 
   const std::string prefix = "Nearby.Share.Transfer.FinalStatus";
   base::UmaHistogramEnumeration(prefix, final_status);
-  base::UmaHistogramEnumeration(
-      prefix + send_or_receive + share_target_type + contact_or_not,
-      final_status);
+  base::UmaHistogramEnumeration(prefix + send_or_receive, final_status);
+  base::UmaHistogramEnumeration(prefix + share_target_type, final_status);
+  base::UmaHistogramEnumeration(prefix + contact_or_not, final_status);
 }

tools/metrics/histograms/histograms_xml/others/histograms.xml

@@ -10213,20 +10213,13 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
   </token>
 </histogram>
 
-<histogram name="Nearby.Share.Transfer.FinalStatus"
-    enum="NearbyShareTransferFinalStatus" expires_after="2021-08-19">
-  <owner>nohle@chromium.org</owner>
-  <owner>nearby-share-chromeos-eng@google.com</owner>
-  <summary>
-    Records the final status of a Nearby Share transfer. Emitted when a transfer
-    completes successfully, fails, or was aborted by the user, for example, by
-    cancelling the transfer.
-  </summary>
-</histogram>
-
 <histogram
     name="Nearby.Share.Transfer.FinalStatus.{Direction}.{ShareTargetType}.{ContactStatus}"
     enum="NearbyShareTransferFinalStatus" expires_after="2021-08-19">
+  <obsolete>
+    Replaced 01/2021 with Nearby.Share.Transfer.FinalStatus{Variation}, which
+    slices by only one dimension.
+  </obsolete>
   <owner>nohle@chromium.org</owner>
   <owner>nearby-share-chromeos-eng@google.com</owner>
   <summary>
@@ -10251,6 +10244,31 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
   </token>
 </histogram>
 
+<histogram name="Nearby.Share.Transfer.FinalStatus{Variation}"
+    enum="NearbyShareTransferFinalStatus" expires_after="2021-08-19">
+  <owner>nohle@chromium.org</owner>
+  <owner>nearby-share-chromeos-eng@google.com</owner>
+  <summary>
+    Records the final status of a Nearby Share transfer {Variation}. Emitted
+    when a transfer completes successfully, fails, or was aborted by the user,
+    for example, by cancelling the transfer.
+  </summary>
+  <token key="Variation">
+    <variant name=""
+        summary="for all sharing scenarios, agnostic of send/receive, device
+                 type, or contact/non-contact"/>
+    <variant name=".Contact" summary="when sharing with a contact"/>
+    <variant name=".Laptop" summary="when sharing with a laptop"/>
+    <variant name=".NonContact" summary="when sharing with a non-contact"/>
+    <variant name=".Phone" summary="when sharing with a phone"/>
+    <variant name=".Receive" summary="when receiving"/>
+    <variant name=".Send" summary="when sending"/>
+    <variant name=".Tablet" summary="when sharing with a tablet"/>
+    <variant name=".UnknownDeviceType"
+        summary="when sharing with an unknown device type"/>
+  </token>
+</histogram>
+
 <histogram name="Nearby.Share.Transfer.NumAttachments{Type}"
     units="attachments" expires_after="2021-08-19">
   <obsolete>