Add UMA Histogram Manager to Cronet.

components/cronet/android/histogram_manager.h

Index: components/cronet/android/histogram_manager.h
diff --git a/components/cronet/android/histogram_manager.h b/components/cronet/android/histogram_manager.h
new file mode 100644
index 0000000000000000000000000000000000000000..ea3ec899ef3e48246f7b702e85c571f2c423f30b
--- /dev/null
+++ b/components/cronet/android/histogram_manager.h
@@ -0,0 +1,64 @@
+// 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.
+
+#ifndef COMPONENTS_CRONET_ANDROID_CRONET_HISTOGRAM_MANAGER_H_
+#define COMPONENTS_CRONET_ANDROID_CRONET_HISTOGRAM_MANAGER_H_
+
+#include <jni.h>
+#include <string>
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+#include "components/metrics/proto/chrome_user_metrics_extension.pb.h"
+
+namespace base {
+class HistogramBase;
+class HistogramBase::Inconsistency
+class HistogramSamples;
+class HistogramSnapshotManager;

[Alexei Svitkine (slow), 2014/12/10 15:19:31]

If these all come from the methods you're overriding from HistogramFlattener,
you don't need to forward declare them, since the header for HistogramFlattener
would already. But you do need to include the header for histogram flattener
since you're inheriting from it...

[ramant (doing other things), 2014/12/10 22:27:51]

Done.

+}  // namespace base
+
+namespace cronet {
+
+bool HistogramManagerRegisterJni(JNIEnv* env);
+
+class HistogramManager : public base::HistogramFlattener {

[Alexei Svitkine (slow), 2014/12/10 15:19:31]

Add a basic comment to the class.

[ramant (doing other things), 2014/12/10 22:27:51]

Done.

+ public:
+  HistogramManager();
+  ~HistogramManager();
+
+  // ---------------------------
+  // HistogramFlattener methods:
+  // ---------------------------
+  void RecordDelta(const base::HistogramBase& histogram,
+                   const base::HistogramSamples& snapshot) override;
+  void InconsistencyDetected(
+      base::HistogramBase::Inconsistency problem) override;
+  void UniqueInconsistencyDetected(
+      base::HistogramBase::Inconsistency problem) override;
+  void InconsistencyDetectedInLoggedCount(int amount) override;
+
+  void PrepareDeltas();
+
+  const metrics::ChromeUserMetricsExtension& uma_proto() const {
+    return uma_proto_;
+  }
+
+ private:
+  void RecordHistogramDelta(const std::string& histogram_name,
+                            const base::HistogramSamples& snapshot);
+
+  base::HistogramSnapshotManager histogram_snapshot_manager_;
+
+  // Stores the protocol buffer representation for this log.
+  metrics::ChromeUserMetricsExtension uma_proto_;
+
+  DISALLOW_COPY_AND_ASSIGN(HistogramManager);
+};
+
+}  // namespace cronet
+
+#endif  // COMPONENTS_CRONET_ANDROID_CRONET_HISTOGRAM_MANAGER_H_