Use size_t for frame count

Change-Id: Idd364443715a920ece2cc54acc95b395b6ed2c6c
diff --git a/jni/rtp/AudioGroup.cpp b/jni/rtp/AudioGroup.cpp
index 1579e6a..2f0829e 100644
--- a/jni/rtp/AudioGroup.cpp
+++ b/jni/rtp/AudioGroup.cpp
@@ -785,8 +785,8 @@
     int deviceSocket = mGroup->mDeviceSocket;
 
     // Find out the frame count for AudioTrack and AudioRecord.
-    int output = 0;
-    int input = 0;
+    size_t output = 0;
+    size_t input = 0;
     if (AudioTrack::getMinFrameCount(&output, AUDIO_STREAM_VOICE_CALL,
         sampleRate) != NO_ERROR || output <= 0 ||
         AudioRecord::getMinFrameCount(&input, sampleRate,