Add a Java API for UMA histograms.

base/android/record_histogram.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 "base/android/jni_android.h"
+#include "base/android/jni_string.h"
+#include "base/android/record_histogram.h"
+#include "base/metrics/histogram.h"
+#include "base/metrics/statistics_recorder.h"
+#include "jni/RecordHistogram_jni.h"
+
+namespace base {
+namespace android {
+
+void RecordBooleanHistogram(JNIEnv* env,
+                            jclass,

[Alexei Svitkine (slow), 2015/01/05 15:54:41]

Nit: I thought Chromium style doesn't permit omitting param names.

[ppi, 2015/01/08 10:54:22]

Done.

+                            jstring j_histogram_name,
+                            jboolean j_sample) {
+  std::string histogram_name = ConvertJavaStringToUTF8(env, j_histogram_name);
+  bool sample = static_cast<bool>(j_sample);
+
+  BooleanHistogram::FactoryGet(histogram_name,
+                               base::HistogramBase::kUmaTargetedHistogramFlag)

[Alexei Svitkine (slow), 2015/01/05 15:54:41]

Nit: This is already in base namespace right, so you don't need the base::
prefix here and elsewhere.

[ppi, 2015/01/08 10:54:22]

Done.

+      ->AddBoolean(sample);
+}
+
+void RecordEnumeratedHistogram(JNIEnv* env,
+                               jclass,
+                               jstring j_histogram_name,
+                               jint j_sample,
+                               jint j_boundary) {
+  std::string histogram_name = ConvertJavaStringToUTF8(env, j_histogram_name);
+  int sample = static_cast<int>(j_sample);
+  int boundary = static_cast<int>(j_boundary);
+
+  base::LinearHistogram::FactoryGet(
+      histogram_name, 1, boundary, boundary + 1,
+      base::HistogramBase::kUmaTargetedHistogramFlag)->Add(sample);
+}
+
+void Initialize(JNIEnv* env, jclass) {
+  StatisticsRecorder::Initialize();
+}
+
+// This backs a Java test util for testing histograms -
+// MetricsUtils.HistogramDelta. It should live in a test-specific file, but we
+// currently can't have test-specific native code packaged in test-specific Java
+// targets - see http://crbug.com/415945.
+jint GetHistogramValueCountForTesting(JNIEnv* env,
+                                      jclass,
+                                      jstring histogram_name,
+                                      jint sample) {
+  base::HistogramBase* histogram = base::StatisticsRecorder::FindHistogram(
+      base::android::ConvertJavaStringToUTF8(env, histogram_name));
+  if (histogram == nullptr) {
+    // No samples have been recorded for this histogram (yet?).
+    return 0;
+  }
+
+  scoped_ptr<base::HistogramSamples> samples = histogram->SnapshotSamples();
+  return samples->GetCount(static_cast<int>(sample));
+}
+
+bool RegisterRecordHistogram(JNIEnv* env) {
+  return RegisterNativesImpl(env);
+}
+
+}  // namespace android
+}  // namespace base