Make UMA stats creation available in the Java interface.

webrtc/system_wrappers/include/metrics_default.h

 /*
  *  Copyright (c) 2016 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_SYSTEM_WRAPPERS_INCLUDE_METRICS_DEFAULT_H_
 #define WEBRTC_SYSTEM_WRAPPERS_INCLUDE_METRICS_DEFAULT_H_
 
 #include <map>
 #include <memory>
 #include <string>
 
 namespace webrtc {
 namespace metrics {
 
+// This class does not actually exist. It is casted to an implementation defined
+// pointer inside the functions.
+class Histogram;
+
 struct SampleInfo {
   SampleInfo(const std::string& name, int min, int max, size_t bucket_count);
   ~SampleInfo();
 
   const std::string name;
   const int min;
   const int max;
   const size_t bucket_count;
   std::map<int, int> samples;  // <value, # of events>
 };
@@ skipping 13 matching lines @@
 
 // Returns the number of times the |sample| has been added to the histogram.
 int NumEvents(const std::string& name, int sample);
 
 // Returns the total number of added samples to the histogram.
 int NumSamples(const std::string& name);
 
 // Returns the minimum sample value (or -1 if the histogram has no samples).
 int MinSample(const std::string& name);
 
+// Function for adding a |sample| to a histogram without checkking the name.
+void HistogramAdd(Histogram* histogram_pointer, int sample);
+
 }  // namespace metrics
 }  // namespace webrtc
 
 #endif  // WEBRTC_SYSTEM_WRAPPERS_INCLUDE_METRICS_DEFAULT_H_