Fix failed capture handling in WebrtcVideoStream

remoting/protocol/webrtc_frame_scheduler_simple.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "remoting/protocol/webrtc_frame_scheduler_simple.h"
 
 #include <algorithm>
 
 #include "remoting/protocol/frame_stats.h"
 #include "remoting/protocol/webrtc_dummy_video_encoder.h"
@@ skipping 160 matching lines @@
   }
 }
 
 bool WebrtcFrameSchedulerSimple::OnFrameCaptured(
     const webrtc::DesktopFrame* frame,
     WebrtcVideoEncoder::FrameParams* params_out) {
   DCHECK(thread_checker_.CalledOnValidThread());
 
   base::TimeTicks now = base::TimeTicks::Now();
 
-  if ((!frame || frame->updated_region().is_empty()) && !top_off_is_active_ &&
-      !key_frame_request_) {
-    frame_pending_ = false;
-    ScheduleNextFrame(now);
-    return false;
+  if ((!frame || frame->updated_region().is_empty())) {
+    bool resend_last_frame =
+        captured_first_frame_ && (top_off_is_active_ || key_frame_request_);
+    if (!resend_last_frame) {

[Jamie, 2017/03/18 01:53:26]

This is pretty complicated logic. I think it would benefit from a comment
explaining what's going on.

[Sergey Ulanov, 2017/03/20 18:24:14]

Done.

+      frame_pending_ = false;
+      ScheduleNextFrame(now);
+      return false;
+    }
   }
 
   if (frame) {
+    captured_first_frame_ = true;
     encoder_bitrate_.SetFrameSize(frame->size());
   }
 
   params_out->bitrate_kbps = encoder_bitrate_.GetTargetBitrateKbps();
   params_out->duration = kTargetFrameInterval;
   params_out->key_frame = key_frame_request_;
   key_frame_request_ = false;
 
   params_out->vpx_min_quantizer = 10;
 
@@ skipping 97 matching lines @@
 void WebrtcFrameSchedulerSimple::CaptureNextFrame() {
   DCHECK(thread_checker_.CalledOnValidThread());
   DCHECK(!frame_pending_);
   last_capture_started_time_ = base::TimeTicks::Now();
   frame_pending_ = true;
   capture_callback_.Run();
 }
 
 }  // namespace protocol
 }  // namespace remoting