Guard against midstream audio configuration changes.

webkit/media/crypto/ppapi/ffmpeg_cdm_audio_decoder.cc

Index: webkit/media/crypto/ppapi/ffmpeg_cdm_audio_decoder.cc
diff --git a/webkit/media/crypto/ppapi/ffmpeg_cdm_audio_decoder.cc b/webkit/media/crypto/ppapi/ffmpeg_cdm_audio_decoder.cc
index e49fa2ba0b5a6c93b3d043aab93e8bb48958638d..2b79e0b0f9f249819853d8c988cc4bd0e71dc614 100644
--- a/webkit/media/crypto/ppapi/ffmpeg_cdm_audio_decoder.cc
+++ b/webkit/media/crypto/ppapi/ffmpeg_cdm_audio_decoder.cc
@@ -87,6 +87,8 @@ FFmpegCdmAudioDecoder::FFmpegCdmAudioDecoder(cdm::Allocator* allocator)
       av_frame_(NULL),
       bits_per_channel_(0),
       samples_per_second_(0),
+      channels_(0),
+      av_sample_format_(0),
       bytes_per_frame_(0),
       last_input_timestamp_(media::kNoTimestamp()),
       output_bytes_to_drop_(0) {
@@ -154,6 +156,10 @@ bool FFmpegCdmAudioDecoder::Initialize(const cdm::AudioDecoderConfig& config) {
   serialized_audio_frames_.reserve(bytes_per_frame_ * samples_per_second_);
   is_initialized_ = true;
 
+  // Store initial values to guard against midstream configuration changes.
+  channels_ = codec_context_->channels;
+  av_sample_format_ = codec_context_->sample_fmt;
+
   return true;
 }
 
@@ -269,10 +275,16 @@ cdm::Status FFmpegCdmAudioDecoder::DecodeBuffer(
 
     int decoded_audio_size = 0;
     if (frame_decoded) {
-      int output_sample_rate = av_frame_->sample_rate;
-      if (output_sample_rate != samples_per_second_) {
-        DLOG(ERROR) << "Output sample rate (" << output_sample_rate
-                    << ") doesn't match expected rate " << samples_per_second_;
+      if (av_frame_->sample_rate != samples_per_second_ ||
+          av_frame_->channels != channels_ ||
+          av_frame_->format != av_sample_format_) {
+        DLOG(ERROR) << "Unsupported midstream configuration change!"
+                    << " Sample Rate: " << av_frame_->sample_rate << " vs "
+                    << samples_per_second_
+                    << ", Channels: " << av_frame_->channels << " vs "
+                    << channels_
+                    << ", Sample Format: " << av_frame_->format << " vs "
+                    << av_sample_format_;
         return cdm::kDecodeError;
       }