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/expand.h b/webrtc/modules/audio_coding/neteq/expand.h
index 3fbafdb..37e58d6 100644
--- a/webrtc/modules/audio_coding/neteq/expand.h
+++ b/webrtc/modules/audio_coding/neteq/expand.h
@@ -64,7 +64,7 @@
 
   // Accessors and mutators.
   virtual size_t overlap_length() const;
-  int16_t max_lag() const { return max_lag_; }
+  size_t max_lag() const { return max_lag_; }
 
  protected:
   static const int kMaxConsecutiveExpands = 200;
@@ -96,11 +96,11 @@
   int consecutive_expands_;
 
  private:
-  static const int kUnvoicedLpcOrder = 6;
-  static const int kNumCorrelationCandidates = 3;
-  static const int kDistortionLength = 20;
-  static const int kLpcAnalysisLength = 160;
-  static const int kMaxSampleRate = 48000;
+  static const size_t kUnvoicedLpcOrder = 6;
+  static const size_t kNumCorrelationCandidates = 3;
+  static const size_t kDistortionLength = 20;
+  static const size_t kLpcAnalysisLength = 160;
+  static const size_t kMaxSampleRate = 48000;
   static const int kNumLags = 3;
 
   struct ChannelParameters {
@@ -132,7 +132,7 @@
   BackgroundNoise* const background_noise_;
   StatisticsCalculator* const statistics_;
   const size_t overlap_length_;
-  int16_t max_lag_;
+  size_t max_lag_;
   size_t expand_lags_[kNumLags];
   int lag_index_direction_;
   int current_lag_index_;