Change DCHECK in VCMDecodedFrameCallback back to just logging.

webrtc/modules/video_coding/generic_decoder.cc

 /*
  *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 41 matching lines @@
                        "timestamp", decodedImage.timestamp());
   // TODO(holmer): We should improve this so that we can handle multiple
   // callbacks from one call to Decode().
   VCMFrameInformation* frameInfo;
   VCMReceiveCallback* callback;
   {
     CriticalSectionScoped cs(_critSect);
     frameInfo = _timestampMap.Pop(decodedImage.timestamp());
     callback = _receiveCallback;
   }
-  RTC_DCHECK(callback != nullptr);
 
   if (frameInfo == NULL) {
     LOG(LS_WARNING) << "Too many frames backed up in the decoder, dropping "
                        "this one.";
     return WEBRTC_VIDEO_CODEC_OK;
   }
 
   const int64_t now_ms = _clock->TimeInMilliseconds();
   if (decode_time_ms < 0) {
     decode_time_ms =
         static_cast<int32_t>(now_ms - frameInfo->decodeStartTimeMs);
   }
   _timing->StopDecodeTimer(decodedImage.timestamp(), decode_time_ms, now_ms,
                            frameInfo->renderTimeMs);
 
   decodedImage.set_render_time_ms(frameInfo->renderTimeMs);
   decodedImage.set_rotation(frameInfo->rotation);
-  callback->FrameToRender(decodedImage);
+  // TODO(sakal): Investigate why callback is NULL sometimes and replace if
+  // statement with a DCHECK.
+  if (callback) {
+    callback->FrameToRender(decodedImage);
+  } else {
+    LOG(LS_WARNING) << "No callback, dropping frame.";
+  }
   return WEBRTC_VIDEO_CODEC_OK;
 }
 
 int32_t VCMDecodedFrameCallback::ReceivedDecodedReferenceFrame(
     const uint64_t pictureId) {
   CriticalSectionScoped cs(_critSect);
   if (_receiveCallback != NULL) {
     return _receiveCallback->ReceivedDecodedReferenceFrame(pictureId);
   }
   return -1;
@@ skipping 89 matching lines @@
 
 bool VCMGenericDecoder::External() const {
   return _isExternal;
 }
 
 bool VCMGenericDecoder::PrefersLateDecoding() const {
   return _decoder->PrefersLateDecoding();
 }
 
 }  // namespace webrtc