Add UMA Histogram Manager to Cronet.

components/metrics/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/metrics/histogram_manager.h"
+
+#include <string>
+#include <vector>
+
+#include "base/memory/singleton.h"
+#include "base/metrics/histogram.h"
+#include "base/metrics/histogram_samples.h"
+#include "components/metrics/histogram_encoder.h"
+
+namespace metrics {
+
+HistogramManager::HistogramManager() : histogram_snapshot_manager_(this) {
+}
+
+HistogramManager::~HistogramManager() {
+}
+
+// static
+HistogramManager* HistogramManager::GetInstance() {
+  return Singleton<HistogramManager>::get();
+}
+
+void HistogramManager::RecordDelta(const base::HistogramBase& histogram,
+                                   const base::HistogramSamples& snapshot) {
+  EncodeHistogramDelta(histogram.histogram_name(), snapshot, &uma_proto_);
+}
+
+void HistogramManager::InconsistencyDetected(
+    base::HistogramBase::Inconsistency problem) {
+  UMA_HISTOGRAM_ENUMERATION("Histogram.InconsistenciesBrowser.Cronet",
+                            problem, base::HistogramBase::NEVER_EXCEEDED_VALUE);
+}
+
+void HistogramManager::UniqueInconsistencyDetected(
+    base::HistogramBase::Inconsistency problem) {
+  UMA_HISTOGRAM_ENUMERATION("Histogram.InconsistenciesBrowserUnique.Cronet",
+                            problem, base::HistogramBase::NEVER_EXCEEDED_VALUE);
+}
+
+void HistogramManager::InconsistencyDetectedInLoggedCount(int amount) {
+  UMA_HISTOGRAM_COUNTS("Histogram.InconsistentSnapshotBrowser.Cronet",
+                       std::abs(amount));
+}
+
+std::vector<uint8> HistogramManager::GetDeltas() {

[mef, 2014/12/11 23:11:41]

should this be HistogramManager::GetDeltas(std::vector<uint8>* data) instead?

[ramant (doing other things), 2014/12/12 02:43:05]

Done.

+  // Clear the protobuf between calls.
+  uma_proto_.Clear();
+  histogram_snapshot_manager_.PrepareDeltas(
+      base::Histogram::kNoFlags, base::Histogram::kUmaTargetedHistogramFlag);
+  int32_t data_size = uma_proto_.ByteSize();
+  std::vector<uint8> data(data_size);
+  if (!uma_proto_.SerializeToArray(&data[0], data_size)) {
+    data.clear();
+  }
+  return data;
+}
+
+}  // namespace metrics