capture_mode: Record histogram for time from screen record length.

This gives a general idea of how long the videos saved on file are. I
looked into adding a test (ps1), but with the multi-threading and async
operations I'm afraid it would be flaky, plus it saved some recording
files locally.

Test: manual
Bug: 1140182
Change-Id: Ib471d6eae0a8c49321984d941fb0775f49ca11a3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2519853Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Commit-Queue: Sammie Quon <sammiequon@chromium.org>
Cr-Commit-Position: refs/heads/master@{#824616}

ash/capture_mode/capture_mode_controller.cc

@@ -50,6 +50,9 @@ CaptureModeController* g_instance = nullptr;
 
 constexpr char kEntryHistogramName[] = "Ash.CaptureModeController.EntryPoint";
 
+constexpr char kRecordTimeHistogramName[] =
+    "Ash.CaptureModeController.ScreenRecordingLength";
+
 constexpr char kScreenCaptureNotificationId[] = "capture_mode_notification";
 constexpr char kScreenCaptureStoppedNotificationId[] =
     "capture_mode_stopped_notification";
@@ -494,12 +497,22 @@ void CaptureModeController::OnVideoFileSaved(bool success) {
 
   // TODO(afakhry): The file will be empty now until the recording service is
   // implemented.
-  if (!success)
+  if (!success) {
     ShowFailureNotification();
-  else
+  } else {
     ShowPreviewNotification(current_video_file_path_, gfx::Image(),
                             CaptureModeType::kVideo);
+    DCHECK(!recording_start_time_.is_null());
+    // Use custom counts macro instead of custom times so we can record in
+    // seconds instead of milliseconds. The max bucket is 3 hours.
+    base::UmaHistogramCustomCounts(
+        kRecordTimeHistogramName,
+        (base::TimeTicks::Now() - recording_start_time_).InSeconds(), /*min=*/1,
+        /*max=*/base::TimeDelta::FromHours(3).InSeconds(),
+        /*bucket_count=*/50);
+  }
 
+  recording_start_time_ = base::TimeTicks();
   current_video_file_path_.clear();
   video_file_handler_.Reset();
 }
@@ -629,6 +642,7 @@ void CaptureModeController::OnVideoRecordCountDownFinished() {
   // in.
   constexpr size_t kVideoBufferCapacityBytes = 20;
   DCHECK(current_video_file_path_.empty());
+  recording_start_time_ = base::TimeTicks::Now();
   current_video_file_path_ = BuildVideoPath(base::Time::Now());
   video_file_handler_ = VideoFileHandler::Create(
       task_runner_, current_video_file_path_, kVideoBufferCapacityBytes);

ash/capture_mode/capture_mode_controller.h

@@ -204,6 +204,11 @@ class ASH_EXPORT CaptureModeController {
   int num_screenshots_taken_in_last_day_ = 0;
   int num_screenshots_taken_in_last_week_ = 0;
 
+  // The time when OnVideoRecordCountDownFinished is called and video has
+  // started recording. It is used when video has finished recording for metrics
+  // collection.
+  base::TimeTicks recording_start_time_;
+
   base::WeakPtrFactory<CaptureModeController> weak_ptr_factory_{this};
 };
 

tools/metrics/histograms/histograms_xml/ash/histograms.xml

@@ -198,6 +198,18 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
   </token>
 </histogram>
 
+<histogram name="Ash.CaptureModeController.ScreenRecordingLength"
+    units="seconds" expires_after="2021-11-04">
+  <owner>afakhry@chromium.org</owner>
+  <owner>chinsenj@chromium.org</owner>
+  <owner>gzadina@google.com</owner>
+  <summary>
+    Records the time of a successful video recording in capture mode. This
+    metric will not be recorded if a file was not successfully saved. The upper
+    limit of this histogram is 3 hours.
+  </summary>
+</histogram>
+
 <histogram name="Ash.CaptureModeController.ScreenshotsPerDay" units="int"
     expires_after="2021-09-29">
   <owner>afakhry@chromium.org</owner>