Create MicCreationSuccessful UMA histogram

Adds a boolean enum histogram to track the frequency at which mic
usage is successful. When mic input is requested in
mediaDevices.getUserMedia(), either a success or failure callback
is run depending on whether a mic was able to be opened. This
histogram logs a success or failure item in each callback.

See http://go/cobalt-mic-uma-histogram for additional details.

b/306441161

cobalt/media_capture/media_devices.cc

@@ -18,6 +18,7 @@
 #include <string>
 #include <utility>
 
+#include "base/metrics/histogram_functions.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "cobalt/base/polymorphic_downcast.h"
 #include "cobalt/media_capture/media_device_info.h"
@@ -66,6 +67,11 @@ std::unique_ptr<Microphone> CreateMicrophone(
   return mic;
 }
 
+void LogMicCreationSucceededHistogramItem(bool mic_creation_succeeded) {
+  base::UmaHistogramBoolean("Cobalt.MediaDevices.MicCreationSucceeded",
+                            mic_creation_succeeded);
+}
+
 }  // namespace.
 
 MediaDevices::MediaDevices(script::EnvironmentSettings* settings,
@@ -169,6 +175,9 @@ void MediaDevices::OnMicrophoneError(
     speech::MicrophoneManager::MicrophoneError error, std::string message) {
   DLOG(INFO) << "MediaDevices::OnMicrophoneError " << message;
 
+  // Log failed mic creation in UMA histogram
+  LogMicCreationSucceededHistogramItem(false);
+
   // No special error handling logic besides logging the message above, so just
   // delegate to the OnMicrophoneStopped() functionality.
   OnMicrophoneStopped();
@@ -195,6 +204,9 @@ void MediaDevices::OnMicrophoneStopped() {
 }
 
 void MediaDevices::OnMicrophoneSuccess() {
+  // Log successful mic creation in UMA histogram
+  LogMicCreationSucceededHistogramItem(true);
+
   if (javascript_message_loop_->task_runner() !=
       base::ThreadTaskRunnerHandle::Get()) {
     javascript_message_loop_->task_runner()->PostTask(

tools/metrics/histograms/metadata/cobalt/histograms.xml

@@ -151,6 +151,19 @@ Always run the pretty print utility on this file after editing:
   </summary>
 </histogram>
 
+<histogram name="Cobalt.MediaDevices.MicCreationSucceeded" enum="Boolean"
+    expires_after="never">
+<!-- expires-never: Needed for long-term tracking of device mic support. -->
+
+  <owner>[email protected]</owner>
+  <owner>[email protected]</owner>
+  <owner>[email protected]</owner>
+  <summary>
+    A boolean representing the success or failure of an attempted mic creation
+    event via mediaDevices.getUserMedia().
+  </summary>
+</histogram>
+
 </histograms>
 
 </histogram-configuration>