Adding a new ChangeLogger class to handle UMA logging of bitrates

webrtc/modules/audio_coding/main/acm2/delayed_logger.cc

+/*
+ *  Copyright (c) 2015 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.
+ */
+
+#include "webrtc/modules/audio_coding/main/acm2/delayed_logger.h"
+#include "webrtc/system_wrappers/interface/metrics.h"
+
+namespace webrtc {
+namespace acm2 {
+
+DelayedLogger::DelayedLogger(const std::string& histogram_name)
+    : value_(0), log_on_next_call_(false), histogram_name_(histogram_name) {

[kwiberg-webrtc, 2015/06/25 09:42:44]

You don't have to initialize value_. (The only significant cost of doing so is
the small while it takes the reader to realize that it isn't necessary.)

+}
+
+DelayedLogger::~DelayedLogger() = default;
+
+void DelayedLogger::SetValue(int value) {
+  value_ = value;
+  log_on_next_call_ = true;
+}
+
+void DelayedLogger::MaybeLogValue() {
+  if (!log_on_next_call_)
+    return;
+
+  RTC_HISTOGRAM_COUNTS_100(histogram_name_, value_);
+  log_on_next_call_ = false;
+}
+
+}  // namespace acm2
+}  // namespace webrtc