NetEq: Fix a bug in expand_rate and speech_expand_rate calculation

webrtc/modules/audio_coding/neteq/merge.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 140 matching lines @@
     (*output)[channel].OverwriteAt(temp_data_.data(), output_length, 0);
   }
 
   // Copy back the first part of the data to |sync_buffer_| and remove it from
   // |output|.
   sync_buffer_->ReplaceAtIndex(*output, old_length, sync_buffer_->next_index());
   output->PopFront(old_length);
 
   // Return new added length. |old_length| samples were borrowed from
   // |sync_buffer_|.
+  RTC_DCHECK_GE(output_length, old_length);
   return output_length - old_length;
 }
 
 size_t Merge::GetExpandedSignal(size_t* old_length, size_t* expand_period) {
   // Check how much data that is left since earlier.
   *old_length = sync_buffer_->FutureLength();
   // Should never be less than overlap_length.
   assert(*old_length >= expand_->overlap_length());
   // Generate data to merge the overlap with using expand.
   expand_->SetParametersForMergeAfterExpand();
@@ skipping 200 matching lines @@
   }
   return best_correlation_index;
 }
 
 size_t Merge::RequiredFutureSamples() {
   return fs_hz_ / 100 * num_channels_;  // 10 ms.
 }
 
 
 }  // namespace webrtc