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/packet_buffer.h b/webrtc/modules/audio_coding/neteq/packet_buffer.h
index d2d429b..737845e 100644
--- a/webrtc/modules/audio_coding/neteq/packet_buffer.h
+++ b/webrtc/modules/audio_coding/neteq/packet_buffer.h
@@ -88,7 +88,7 @@
   // Subsequent packets with the same timestamp as the one extracted will be
   // discarded and properly deleted. The number of discarded packets will be
   // written to the output variable |discard_count|.
-  virtual Packet* GetNextPacket(int* discard_count);
+  virtual Packet* GetNextPacket(size_t* discard_count);
 
   // Discards the first packet in the buffer. The packet is deleted.
   // Returns PacketBuffer::kBufferEmpty if the buffer is empty,
@@ -109,12 +109,12 @@
 
   // Returns the number of packets in the buffer, including duplicates and
   // redundant packets.
-  virtual int NumPacketsInBuffer() const;
+  virtual size_t NumPacketsInBuffer() const;
 
   // Returns the number of samples in the buffer, including samples carried in
   // duplicate and redundant packets.
-  virtual int NumSamplesInBuffer(DecoderDatabase* decoder_database,
-                                 int last_decoded_length) const;
+  virtual size_t NumSamplesInBuffer(DecoderDatabase* decoder_database,
+                                    size_t last_decoded_length) const;
 
   // Increase the waiting time counter for every packet in the buffer by |inc|.
   // The default value for |inc| is 1.