Update a ton of audio code to use size_t more correctly and in general reduce
use of int16_t/uint16_t.

This is the upshot of a recommendation by henrik.lundin and kwiberg on an original small change ( https://webrtc-codereview.appspot.com/42569004/#ps1 ) to stop using int16_t just because values could fit in it, and is similar in nature to a previous "mass change to use size_t more" ( https://webrtc-codereview.appspot.com/23129004/ ) which also needed to be split up for review but to land all at once, since, like adding "const", such changes tend to cause a lot of transitive effects.

This was be reviewed and approved in pieces:
https://codereview.webrtc.org/1224093003
https://codereview.webrtc.org/1224123002
https://codereview.webrtc.org/1224163002
https://codereview.webrtc.org/1225133003
https://codereview.webrtc.org/1225173002
https://codereview.webrtc.org/1227163003
https://codereview.webrtc.org/1227203003
https://codereview.webrtc.org/1227213002
https://codereview.webrtc.org/1227893002
https://codereview.webrtc.org/1228793004
https://codereview.webrtc.org/1228803003
https://codereview.webrtc.org/1228823002
https://codereview.webrtc.org/1228823003
https://codereview.webrtc.org/1228843002
https://codereview.webrtc.org/1230693002
https://codereview.webrtc.org/1231713002

The change is being landed as TBR to all the folks who reviewed the above.

BUG=chromium:81439
TEST=none
R=andrew@webrtc.org, pbos@webrtc.org
TBR=aluebs, andrew, asapersson, henrika, hlundin, jan.skoglund, kwiberg, minyue, pbos, pthatcher

Review URL: https://codereview.webrtc.org/1230503003 .

Cr-Commit-Position: refs/heads/master@{#9768}
diff --git a/webrtc/modules/audio_coding/neteq/merge.h b/webrtc/modules/audio_coding/neteq/merge.h
index 1b60aec..727e9a6 100644
--- a/webrtc/modules/audio_coding/neteq/merge.h
+++ b/webrtc/modules/audio_coding/neteq/merge.h
@@ -46,11 +46,11 @@
   // de-interleaving |input|. The values in |external_mute_factor_array| (Q14)
   // will be used to scale the audio, and is updated in the process. The array
   // must have |num_channels_| elements.
-  virtual int Process(int16_t* input, size_t input_length,
-                      int16_t* external_mute_factor_array,
-                      AudioMultiVector* output);
+  virtual size_t Process(int16_t* input, size_t input_length,
+                         int16_t* external_mute_factor_array,
+                         AudioMultiVector* output);
 
-  virtual int RequiredFutureSamples();
+  virtual size_t RequiredFutureSamples();
 
  protected:
   const int fs_hz_;
@@ -58,38 +58,38 @@
 
  private:
   static const int kMaxSampleRate = 48000;
-  static const int kExpandDownsampLength = 100;
-  static const int kInputDownsampLength = 40;
-  static const int kMaxCorrelationLength = 60;
+  static const size_t kExpandDownsampLength = 100;
+  static const size_t kInputDownsampLength = 40;
+  static const size_t kMaxCorrelationLength = 60;
 
   // Calls |expand_| to get more expansion data to merge with. The data is
   // written to |expanded_signal_|. Returns the length of the expanded data,
   // while |expand_period| will be the number of samples in one expansion period
   // (typically one pitch period). The value of |old_length| will be the number
   // of samples that were taken from the |sync_buffer_|.
-  int GetExpandedSignal(int* old_length, int* expand_period);
+  size_t GetExpandedSignal(size_t* old_length, size_t* expand_period);
 
   // Analyzes |input| and |expanded_signal| to find maximum values. Returns
   // a muting factor (Q14) to be used on the new data.
-  int16_t SignalScaling(const int16_t* input, int input_length,
+  int16_t SignalScaling(const int16_t* input, size_t input_length,
                         const int16_t* expanded_signal,
                         int16_t* expanded_max, int16_t* input_max) const;
 
   // Downsamples |input| (|input_length| samples) and |expanded_signal| to
   // 4 kHz sample rate. The downsampled signals are written to
   // |input_downsampled_| and |expanded_downsampled_|, respectively.
-  void Downsample(const int16_t* input, int input_length,
-                  const int16_t* expanded_signal, int expanded_length);
+  void Downsample(const int16_t* input, size_t input_length,
+                  const int16_t* expanded_signal, size_t expanded_length);
 
   // Calculates cross-correlation between |input_downsampled_| and
   // |expanded_downsampled_|, and finds the correlation maximum. The maximizing
   // lag is returned.
-  int16_t CorrelateAndPeakSearch(int16_t expanded_max, int16_t input_max,
-                                 int start_position, int input_length,
-                                 int expand_period) const;
+  size_t CorrelateAndPeakSearch(int16_t expanded_max, int16_t input_max,
+                                size_t start_position, size_t input_length,
+                                size_t expand_period) const;
 
   const int fs_mult_;  // fs_hz_ / 8000.
-  const int timestamps_per_call_;
+  const size_t timestamps_per_call_;
   Expand* expand_;
   SyncBuffer* sync_buffer_;
   int16_t expanded_downsampled_[kExpandDownsampLength];