Update audio code to use size_t more correctly,

webrtc/modules/audio_coding/neteq/dtmf_tone_generator.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 131 matching lines @@
   initialized_ = true;
   return 0;
 }
 
 // Reset tone generator to uninitialized state.
 void DtmfToneGenerator::Reset() {
   initialized_ = false;
 }
 
 // Generate num_samples of DTMF signal and write to |output|.
-int DtmfToneGenerator::Generate(int num_samples,
+int DtmfToneGenerator::Generate(size_t num_samples,
                                 AudioMultiVector* output) {
   if (!initialized_) {
     return kNotInitialized;
   }
 
-  if (num_samples < 0 || !output) {
+  if (!output) {
     return kParameterError;
   }
 
   output->AssertSize(num_samples);
-  for (int i = 0; i < num_samples; ++i) {
+  for (size_t i = 0; i < num_samples; ++i) {
     // Use recursion formula y[n] = a * y[n - 1] - y[n - 2].
     int16_t temp_val_low = ((coeff1_ * sample_history1_[1] + 8192) >> 14)
         - sample_history1_[0];
     int16_t temp_val_high = ((coeff2_ * sample_history2_[1] + 8192) >> 14)
         - sample_history2_[0];
 
     // Update recursion memory.
     sample_history1_[0] = sample_history1_[1];
     sample_history1_[1] = temp_val_low;
     sample_history2_[0] = sample_history2_[1];
     sample_history2_[1] = temp_val_high;
 
     // Attenuate the low frequency tone 3 dB.
     int32_t temp_val = kAmpMultiplier * temp_val_low + (temp_val_high << 15);
     // Normalize the signal to Q14 with proper rounding.
     temp_val = (temp_val + 16384) >> 15;
     // Scale the signal to correct volume.
     (*output)[0][i] =
         static_cast<int16_t>((temp_val * amplitude_ + 8192) >> 14);
   }
   // Copy first channel to all other channels.
   for (size_t channel = 1; channel < output->Channels(); ++channel) {
     output->CopyChannel(0, channel);
   }
 
-  return num_samples;
+  return static_cast<int>(num_samples);
 }
 
 bool DtmfToneGenerator::initialized() const {
   return initialized_;
 }
 
 }  // namespace webrtc