Adjust VideoCaptureOracle wrt. out of order captures.

content/browser/media/capture/video_capture_oracle.cc

Index: content/browser/media/capture/video_capture_oracle.cc
diff --git a/content/browser/media/capture/video_capture_oracle.cc b/content/browser/media/capture/video_capture_oracle.cc
index 9157d8ce002f34997ccb0918ec7fc9aff323fe32..0632ef1313c1b9ad7d3e2e67096cb1a323b98861 100644
--- a/content/browser/media/capture/video_capture_oracle.cc
+++ b/content/browser/media/capture/video_capture_oracle.cc
@@ -38,7 +38,8 @@ double FractionFromExpectedFrameRate(base::TimeDelta delta, int frame_rate) {
 
 VideoCaptureOracle::VideoCaptureOracle(base::TimeDelta min_capture_period)
     : next_frame_number_(0),
-      last_delivered_frame_number_(-1),
+      last_successfully_delivered_frame_number_(-1),
+      num_frames_pending_(0),
       smoothing_sampler_(min_capture_period,
                          kNumRedundantCapturesOfStaticContent),
       content_sampler_(min_capture_period) {
@@ -80,7 +81,7 @@ bool VideoCaptureOracle::ObserveEventAndDecideCapture(
     case kTimerPoll:
       // While the timer is firing, only allow a sampling if there are none
       // currently in-progress.
-      if (last_delivered_frame_number_ == (next_frame_number_ - 1)) {
+      if (num_frames_pending_ == 0) {
         should_sample = smoothing_sampler_.IsOverdueForSamplingAt(event_time);
         if (should_sample)
           duration_of_next_frame_ = smoothing_sampler_.min_capture_period();
@@ -98,28 +99,32 @@ bool VideoCaptureOracle::ObserveEventAndDecideCapture(
 int VideoCaptureOracle::RecordCapture() {
   smoothing_sampler_.RecordSample();
   content_sampler_.RecordSample(GetFrameTimestamp(next_frame_number_));
+  num_frames_pending_++;
   return next_frame_number_++;
 }
 
 bool VideoCaptureOracle::CompleteCapture(int frame_number,
                                          bool capture_was_successful,
                                          base::TimeTicks* frame_timestamp) {
-  // Drop frame if previous frame number is higher.
-  if (last_delivered_frame_number_ > frame_number) {
+  num_frames_pending_--;
+
+  // Drop frame if previously delivered frame number is higher.
+  if (last_successfully_delivered_frame_number_ > frame_number) {
     LOG_IF(WARNING, capture_was_successful)
         << "Out of order frame delivery detected (have #" << frame_number
-        << ", last was #" << last_delivered_frame_number_
+        << ", last was #" << last_successfully_delivered_frame_number_
         << ").  Dropping frame.";
     return false;
   }
-  DCHECK_NE(last_delivered_frame_number_, frame_number);
-  last_delivered_frame_number_ = frame_number;
 
   if (!capture_was_successful) {
     VLOG(2) << "Capture of frame #" << frame_number << " was not successful.";
     return false;
   }
 
+  DCHECK_NE(last_successfully_delivered_frame_number_, frame_number);
+  last_successfully_delivered_frame_number_ = frame_number;
+
   *frame_timestamp = GetFrameTimestamp(frame_number);
 
   // If enabled, log a measurement of how this frame timestamp has incremented