Adding Media.InputStreamDuration to UMA histograms for low-latency input audio streams.

My idea was that the histogram could show if we do a very large number of short
calls and how the length of the streams are related to the length of
AudioTracks. If so, we might have issues in WebRTC clients or in how we
create/destroy the input streams.

BUG=405449
TEST=Manual testing using WebRTC clients.

Review URL: https://codereview.chromium.org/537573002

Cr-Commit-Position: refs/heads/master@{#293496}

media/audio/audio_input_controller.cc

@@ -5,6 +5,7 @@
 #include "media/audio/audio_input_controller.h"
 
 #include "base/bind.h"
+#include "base/strings/string_number_conversions.h"
 #include "base/strings/stringprintf.h"
 #include "base/threading/thread_restrictions.h"
 #include "base/time/time.h"
@@ -263,6 +264,7 @@ void AudioInputController::DoCreateForLowLatency(AudioManager* audio_manager,
     log_silence_state_ = true;
 #endif
 
+  low_latency_create_time_ = base::TimeTicks::Now();
   DoCreate(audio_manager, params, device_id);
 }
 
@@ -347,8 +349,20 @@ void AudioInputController::DoClose() {
   if (state_ == CLOSED)
     return;
 
-  if (handler_)
-    handler_->OnLog(this, "AIC::DoClose");
+  // If this is a low-latency stream, log the total duration (since DoCreate)
+  // and add it to a UMA histogram.
+  if (!low_latency_create_time_.is_null()) {
+    base::TimeDelta duration =
+        base::TimeTicks::Now() - low_latency_create_time_;
+    UMA_HISTOGRAM_LONG_TIMES("Media.InputStreamDuration", duration);
+    if (handler_) {
+      std::string log_string =
+          base::StringPrintf("AIC::DoClose: stream duration=");
+      log_string += base::Int64ToString(duration.InSeconds());
+      log_string += " seconds";
+      handler_->OnLog(this, log_string);
+    }
+  }
 
   // Delete the timer on the same thread that created it.
   no_data_timer_.reset();

media/audio/audio_input_controller.h

@@ -369,6 +369,9 @@ class MEDIA_EXPORT AudioInputController
 
   size_t prev_key_down_count_;
 
+  // Time when a low-latency stream is created.
+  base::TimeTicks low_latency_create_time_;
+
   DISALLOW_COPY_AND_ASSIGN(AudioInputController);
 };
 

tools/metrics/histograms/histograms.xml

@@ -11460,6 +11460,14 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="Media.InputStreamDuration" units="ms">
+  <owner>henrika@chromium.org</owner>
+  <summary>
+    Duration in milliseconds of low-latency audio input streams. Sampled when
+    the stream is closed by the AudioInputController.
+  </summary>
+</histogram>
+
 <histogram name="Media.LinuxAudioIO" enum="LinuxAudioIO">
   <owner>dalecurtis@chromium.org</owner>
   <summary>