Adding defensive CHECKs for AudioDecoderConfig crash

media/filters/source_buffer_stream.cc

Index: media/filters/source_buffer_stream.cc
diff --git a/media/filters/source_buffer_stream.cc b/media/filters/source_buffer_stream.cc
index 895df15f263c7df9bc11ed918029ab6ec23d4289..be4f1c11461253b895d3f79e89d29ccbf54e5d1a 100644
--- a/media/filters/source_buffer_stream.cc
+++ b/media/filters/source_buffer_stream.cc
@@ -1551,12 +1551,18 @@ bool SourceBufferStream::IsEndOfStreamReached() const {
 const AudioDecoderConfig& SourceBufferStream::GetCurrentAudioDecoderConfig() {
   if (config_change_pending_)
     CompleteConfigChange();
+  // Trying to track down crash. http://crbug.com/715761
+  CHECK(current_config_index_ >= 0 &&
+        static_cast<size_t>(current_config_index_) < audio_configs_.size());
   return audio_configs_[current_config_index_];
 }
 
 const VideoDecoderConfig& SourceBufferStream::GetCurrentVideoDecoderConfig() {
   if (config_change_pending_)
     CompleteConfigChange();
+  // Trying to track down crash. http://crbug.com/715761
+  CHECK(current_config_index_ >= 0 &&
+        static_cast<size_t>(current_config_index_) < video_configs_.size());
   return video_configs_[current_config_index_];
 }