Add UMA Histogram Manager to Cronet.

components/cronet/android/histogram_manager.cc

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/cronet/android/histogram_manager.h"
+
+#include <string>
+#include <vector>
+
+#include "base/android/jni_array.h"
+#include "components/metrics/histogram_manager.h"
+
+#include "jni/HistogramManager_jni.h"
+
+namespace cronet {
+
+// Explicitly register static JNI functions.
+bool HistogramManagerRegisterJni(JNIEnv* env) {
+  return RegisterNativesImpl(env);
+}
+
+static jbyteArray GetHistogramDeltas(JNIEnv* env, jobject jcaller) {
+  std::vector<uint8> data;
+  if (!metrics::HistogramManager::GetInstance()->GetDeltas(&data))
+    return NULL;
+  return base::android::ToJavaByteArray(env, &data[0], data.size()).Release();
+}
+
+}  // namespace cronet