ReceiveStatisticsProxy: add some unit tests, change members from int to int64_t.

webrtc/video/receive_statistics_proxy.cc

 /*
  *  Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 424 matching lines @@
     rtc::CritScope lock(&crit_);
     qp_sample_.Add(encoded_image.qp_);
   }
 }
 
 void ReceiveStatisticsProxy::SampleCounter::Add(int sample) {
   sum += sample;
   ++num_samples;
 }
 
-int ReceiveStatisticsProxy::SampleCounter::Avg(int min_required_samples) const {
+int ReceiveStatisticsProxy::SampleCounter::Avg(
+    int64_t min_required_samples) const {
   if (num_samples < min_required_samples || num_samples == 0)
     return -1;
-  return sum / num_samples;
+  return static_cast<int>(sum / num_samples);
 }
 
 void ReceiveStatisticsProxy::SampleCounter::Reset() {
   num_samples = 0;
   sum = 0;
 }
 
 }  // namespace webrtc