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.cc b/webrtc/modules/audio_processing/audio_buffer.cc
index 6f73262..81790a1 100644
--- a/webrtc/modules/audio_processing/audio_buffer.cc
+++ b/webrtc/modules/audio_processing/audio_buffer.cc
@@ -19,9 +19,9 @@
 namespace webrtc {
 namespace {
 
-const int kSamplesPer16kHzChannel = 160;
-const int kSamplesPer32kHzChannel = 320;
-const int kSamplesPer48kHzChannel = 480;
+const size_t kSamplesPer16kHzChannel = 160;
+const size_t kSamplesPer32kHzChannel = 320;
+const size_t kSamplesPer48kHzChannel = 480;
 
 int KeyboardChannelIndex(const StreamConfig& stream_config) {
   if (!stream_config.has_keyboard()) {
@@ -32,23 +32,22 @@
   return stream_config.num_channels();
 }
 
-int NumBandsFromSamplesPerChannel(int num_frames) {
-  int num_bands = 1;
+size_t NumBandsFromSamplesPerChannel(size_t num_frames) {
+  size_t num_bands = 1;
   if (num_frames == kSamplesPer32kHzChannel ||
       num_frames == kSamplesPer48kHzChannel) {
-    num_bands = rtc::CheckedDivExact(num_frames,
-                                     static_cast<int>(kSamplesPer16kHzChannel));
+    num_bands = rtc::CheckedDivExact(num_frames, kSamplesPer16kHzChannel);
   }
   return num_bands;
 }
 
 }  // namespace
 
-AudioBuffer::AudioBuffer(int input_num_frames,
+AudioBuffer::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)
   : input_num_frames_(input_num_frames),
     num_input_channels_(num_input_channels),
     proc_num_frames_(process_num_frames),
@@ -345,20 +344,20 @@
   num_channels_ = num_channels;
 }
 
-int AudioBuffer::num_frames() const {
+size_t AudioBuffer::num_frames() const {
   return proc_num_frames_;
 }
 
-int AudioBuffer::num_frames_per_band() const {
+size_t AudioBuffer::num_frames_per_band() const {
   return num_split_frames_;
 }
 
-int AudioBuffer::num_keyboard_frames() const {
+size_t AudioBuffer::num_keyboard_frames() const {
   // We don't resample the keyboard channel.
   return input_num_frames_;
 }
 
-int AudioBuffer::num_bands() const {
+size_t AudioBuffer::num_bands() const {
   return num_bands_;
 }