[TTS] Add aggregation of CTR metrics to the CS component.

components/contextual_search/browser/device_int_storage.h

Index: components/contextual_search/browser/device_int_storage.h
diff --git a/components/contextual_search/browser/device_int_storage.h b/components/contextual_search/browser/device_int_storage.h
new file mode 100644
index 0000000000000000000000000000000000000000..4c3d0bfffb46b397da560dc3626750e3bf623e6c
--- /dev/null
+++ b/components/contextual_search/browser/device_int_storage.h
@@ -0,0 +1,33 @@
+// Copyright 2016 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_CONTEXTUAL_SEARCH_BROWSER_DEVICE_INT_STORAGE_H_
+#define COMPONENTS_CONTEXTUAL_SEARCH_BROWSER_DEVICE_INT_STORAGE_H_
+
+#include <string>
+
+#include "base/macros.h"
+
+namespace contextual_search {
+
+// Interface for device-specific integer storage.
+// Allows callers to read and write integers to persistent storage on the
+// device.
+class DeviceIntStorage {
+ public:
+  DeviceIntStorage() {}
+  virtual ~DeviceIntStorage() {}
+
+  // Reads and returns the integer keyed by |storage_key|
+  virtual int ReadInt(std::string storage_key) = 0;
+  // Writes the integer |value| to the storage bin keyed by |storage_key|.
+  virtual void WriteInt(std::string storage_key, int value) = 0;
+

[marq (ping after 24h), 2016/08/30 08:30:36]

If this class is intended to be an abstraction layer that could be backed by
(for example) Prefs values, then there should also be a Clear() method that
removes the storage bucket. 

[Donn Denman, 2016/08/31 04:35:21]

Done.

+ private:
+  DISALLOW_COPY_AND_ASSIGN(DeviceIntStorage);
+};
+
+}  // namespace contextual_search
+
+#endif  // COMPONENTS_CONTEXTUAL_SEARCH_BROWSER_DEVICE_INT_STORAGE_H_