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/utility/source/file_player_impl.cc b/webrtc/modules/utility/source/file_player_impl.cc
index df6a5bf..8c94caa 100644
--- a/webrtc/modules/utility/source/file_player_impl.cc
+++ b/webrtc/modules/utility/source/file_player_impl.cc
@@ -95,7 +95,7 @@
 
 int32_t FilePlayerImpl::Get10msAudioFromFile(
     int16_t* outBuffer,
-    int& lengthInSamples,
+    size_t& lengthInSamples,
     int frequencyInHz)
 {
     if(_codec.plfreq == 0)
@@ -127,8 +127,7 @@
             return 0;
         }
         // One sample is two bytes.
-        unresampledAudioFrame.samples_per_channel_ =
-            (uint16_t)lengthInBytes >> 1;
+        unresampledAudioFrame.samples_per_channel_ = lengthInBytes >> 1;
 
     } else {
         // Decode will generate 10 ms of audio data. PlayoutAudioData(..)
@@ -156,14 +155,14 @@
         }
     }
 
-    int outLen = 0;
+    size_t outLen = 0;
     if(_resampler.ResetIfNeeded(unresampledAudioFrame.sample_rate_hz_,
                                 frequencyInHz, 1))
     {
         LOG(LS_WARNING) << "Get10msAudioFromFile() unexpected codec.";
 
         // New sampling frequency. Update state.
-        outLen = frequencyInHz / 100;
+        outLen = static_cast<size_t>(frequencyInHz / 100);
         memset(outBuffer, 0, outLen * sizeof(int16_t));
         return 0;
     }
@@ -177,7 +176,7 @@
 
     if(_scaling != 1.0)
     {
-        for (int i = 0;i < outLen; i++)
+        for (size_t i = 0;i < outLen; i++)
         {
             outBuffer[i] = (int16_t)(outBuffer[i] * _scaling);
         }