Allow custom metrics implementations on Android.

webrtc/api/android/jni/androidhistogram_jni.cc

+/*
+ *  Copyright 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.
+ */
+
+#include <map>
+#include <memory>
+
+#include "webrtc/api/android/jni/classreferenceholder.h"
+#include "webrtc/api/android/jni/jni_helpers.h"
+#include "webrtc/api/android/jni/native_handle_impl.h"
+#include "webrtc/system_wrappers/include/metrics.h"
+
+// Enables collection of native histograms and creating them.
+namespace webrtc_jni {
+
+JOW(jlong, Histogram_nativeCreateCounts)
+(JNIEnv* jni, jclass, jstring j_name, jint min, jint max, jint buckets) {
+  std::string name = JavaToStdString(jni, j_name);
+  return jlongFromPointer(
+      webrtc::metrics::HistogramFactoryGetCounts(name, min, max, buckets));
+}
+
+JOW(void, Histogram_nativeAddSample)
+(JNIEnv* jni, jclass, jlong histogram, jint sample) {
+  if (histogram) {
+    HistogramAdd(reinterpret_cast<webrtc::metrics::Histogram*>(histogram),
+                 sample);
+  }
+}
+}