Add UMA Histogram Manager to Cronet.

components/cronet/android/histogram_manager.cc

Index: components/cronet/android/histogram_manager.cc
diff --git a/components/cronet/android/histogram_manager.cc b/components/cronet/android/histogram_manager.cc
new file mode 100644
index 0000000000000000000000000000000000000000..32622c2b88c97464ec6dfe519e18979a3c1739f1
--- /dev/null
+++ b/components/cronet/android/histogram_manager.cc
@@ -0,0 +1,31 @@
+// 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);
+}
+
+jbyteArray GetHistogramDeltas(JNIEnv* env, jobject jcaller) {
+  std::vector<uint8> data =
+      metrics::HistogramManager::GetInstance()->GetDeltas();
+  if (!data.empty()) {
+    return base::android::ToJavaByteArray(env, &data[0], data.size()).Release();
+  }
+  return NULL;
+}
+
+}  // namespace cronet