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_processing/audio_buffer.h b/webrtc/modules/audio_processing/audio_buffer.h
index aeb303b..f82ab61 100644
--- a/webrtc/modules/audio_processing/audio_buffer.h
+++ b/webrtc/modules/audio_processing/audio_buffer.h
@@ -33,19 +33,19 @@
 class AudioBuffer {
  public:
   // TODO(ajm): Switch to take ChannelLayouts.
-  AudioBuffer(int input_num_frames,
+  AudioBuffer(size_t input_num_frames,
               int num_input_channels,
-              int process_num_frames,
+              size_t process_num_frames,
               int num_process_channels,
-              int output_num_frames);
+              size_t output_num_frames);
   virtual ~AudioBuffer();
 
   int num_channels() const;
   void set_num_channels(int num_channels);
-  int num_frames() const;
-  int num_frames_per_band() const;
-  int num_keyboard_frames() const;
-  int num_bands() const;
+  size_t num_frames() const;
+  size_t num_frames_per_band() const;
+  size_t num_keyboard_frames() const;
+  size_t num_bands() const;
 
   // Returns a pointer array to the full-band channels.
   // Usage:
@@ -127,20 +127,20 @@
 
   // The audio is passed into DeinterleaveFrom() or CopyFrom() with input
   // format (samples per channel and number of channels).
-  const int input_num_frames_;
+  const size_t input_num_frames_;
   const int num_input_channels_;
   // The audio is stored by DeinterleaveFrom() or CopyFrom() with processing
   // format.
-  const int proc_num_frames_;
+  const size_t proc_num_frames_;
   const int num_proc_channels_;
   // The audio is returned by InterleaveTo() and CopyTo() with output samples
   // per channels and the current number of channels. This last one can be
   // changed at any time using set_num_channels().
-  const int output_num_frames_;
+  const size_t output_num_frames_;
   int num_channels_;
 
-  int num_bands_;
-  int num_split_frames_;
+  size_t num_bands_;
+  size_t num_split_frames_;
   bool mixed_low_pass_valid_;
   bool reference_copied_;
   AudioFrame::VADActivity activity_;