Adding a new ChangeLogger class to handle UMA logging of bitrates

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

+/*
+ *  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.
+ */
+
+#ifndef WEBRTC_MODULES_AUDIO_CODING_MAIN_ACM2_DELAYED_LOGGER_H_
+#define WEBRTC_MODULES_AUDIO_CODING_MAIN_ACM2_DELAYED_LOGGER_H_
+
+#include <string>
+
+#include "webrtc/base/constructormagic.h"
+
+namespace webrtc {
+namespace acm2 {
+
+// This class handles logging of values to histograms. Registering new values
+// and writing to histogram is handled by separate functions.
+class DelayedLogger {
+ public:
+  explicit DelayedLogger(const std::string& histogram_name);
+  ~DelayedLogger();
+
+  // Logs a new value locally in the DelayedLogger object. Nothing is written
+  // to the histogram from this function. The value will be written on the next
+  // call to MaybeLogTargetBitrate.
+  void SetValue(int value);

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

It isn't clear from this description that a second call will overwrite the value
set by the first. Maybe change the first sentence to

  "Sets a new value locally in the DelayedLogger object (overwriting any
previous value)."

+
+  // Writes value to histogram, if SetValue was called since the last invocation
+  // of MaybeLogValue. If not, this function does nothing.
+  void MaybeLogValue();

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

You don't suppress logging of a value that's identical to the previous logged
value. Is that what you want for this application?

+
+ private:
+  int value_;
+  bool log_on_next_call_;
+  const std::string histogram_name_;
+
+  DISALLOW_COPY_AND_ASSIGN(DelayedLogger);
+};
+
+}  // namespace acm2
+}  // namespace webrtc
+#endif  // WEBRTC_MODULES_AUDIO_CODING_MAIN_ACM2_DELAYED_LOGGER_H_