[CrOS PhoneHub] Add metrics for message sending success rate.

Add MultiDevice.SecureChannel.Nearby.SendMessageResult histogram.

Bug: 1106937, 1150634
Change-Id: I23464231392275845e8e2c60c8edfbcd02d01ee4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2566977Reviewed-by: Mark Pearson <mpearson@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Commit-Queue: Andre Le <leandre@chromium.org>
Cr-Commit-Position: refs/heads/master@{#833617}

chrome/browser/chromeos/secure_channel/nearby_connection_broker_impl.cc

@@ -5,6 +5,7 @@
 #include "chrome/browser/chromeos/secure_channel/nearby_connection_broker_impl.h"
 
 #include "base/memory/ptr_util.h"
+#include "base/metrics/histogram_functions.h"
 #include "base/rand_util.h"
 #include "chrome/browser/chromeos/secure_channel/nearby_endpoint_finder.h"
 #include "chromeos/components/multidevice/logging/logging.h"
@@ -196,6 +197,9 @@ void NearbyConnectionBrokerImpl::OnSendPayloadResult(
   bool success = status == Status::kSuccess;
   std::move(callback).Run(success);
 
+  base::UmaHistogramBoolean(
+      "MultiDevice.SecureChannel.Nearby.SendMessageResult", success);
+
   if (success)
     return;
 

tools/metrics/histograms/histograms_xml/multi_device/histograms.xml

@@ -248,6 +248,17 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
   </summary>
 </histogram>
 
+<histogram name="MultiDevice.SecureChannel.Nearby.SendMessageResult"
+    enum="BooleanSuccess" expires_after="2021-11-30">
+  <owner>khorimoto@chromium.org</owner>
+  <owner>better-together-dev@google.com</owner>
+  <summary>
+    Measures the success rate of sending a SecureChannel message via the Nearby
+    Connections library. Emitted when the Nearby Connections library sends a
+    message.
+  </summary>
+</histogram>
+
 <histogram name="MultiDevice.Setup.HostStatus"
     enum="MultiDevice_Setup_HostStatus" expires_after="2021-04-04">
   <owner>vecore@google.com</owner>