Implement NullVideoDecoder to avoid crash on unsupported decoders.

webrtc/video_decoder.h

 /*
  *  Copyright (c) 2014 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 104 matching lines @@
   const DecoderType decoder_type_;
   VideoDecoder* const decoder_;
 
   VideoCodec codec_settings_;
   int32_t number_of_cores_;
   std::string fallback_implementation_name_;
   rtc::scoped_ptr<VideoDecoder> fallback_decoder_;
   DecodedImageCallback* callback_;
 };
 
+// Video decoder class to be used for unknown codecs. Doesn't support decoding
+// but logs messages to LS_ERROR.
+class NullVideoDecoder : public VideoDecoder {
+ public:
+  NullVideoDecoder();
+
+  int32_t InitDecode(const VideoCodec* codec_settings,
+                     int32_t number_of_cores) override;
+
+  int32_t Decode(const EncodedImage& input_image,
+                 bool missing_frames,
+                 const RTPFragmentationHeader* fragmentation,
+                 const CodecSpecificInfo* codec_specific_info,
+                 int64_t render_time_ms) override;
+
+  int32_t RegisterDecodeCompleteCallback(
+      DecodedImageCallback* callback) override;
+
+  int32_t Release() override;
+  int32_t Reset() override;
+
+  const char* ImplementationName() const override;
+};
+
 }  // namespace webrtc
 
 #endif  // WEBRTC_VIDEO_DECODER_H_