Refactor HashedExtensionMetrics into ExtensionsMetricsProvider.

chrome/browser/metrics/extension_metrics.h

-// 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 CHROME_BROWSER_METRICS_EXTENSION_METRICS_H_
-#define CHROME_BROWSER_METRICS_EXTENSION_METRICS_H_
-
-#include <string>
-
-#include "base/basictypes.h"
-#include "base/memory/scoped_ptr.h"
-
-class Profile;
-
-namespace extensions {
-class ExtensionSet;
-}
-
-namespace metrics {
-class SystemProfileProto;
-}
-
-// HashedExtensionMetrics groups various constants and functions used for
-// reporting extension IDs with UMA reports (after hashing the extension IDs
-// for privacy).
-class HashedExtensionMetrics {
- public:
-  explicit HashedExtensionMetrics(uint64 client_id);
-  virtual ~HashedExtensionMetrics();
-
-  // Writes the hashed list of installed extensions into the specified
-  // SystemProfileProto object.
-  void WriteExtensionList(metrics::SystemProfileProto* system_profile);
-
- protected:
-  // Retrieves the set of extensions installed in the current profile.  The
-  // default implementation should be fine, but this can be overridden for
-  // testing.
-  //
-  // TODO(mvrable): If metrics are ever converted to being per-profile, then
-  // this should be updated to return extensions installed in a specified
-  // profile.
-  virtual scoped_ptr<extensions::ExtensionSet> GetInstalledExtensions();
-
-  // Hashes the extension extension ID using the provided client key (which
-  // must be less than kExtensionListClientKeys) and to produce an output value
-  // between 0 and kExtensionListBuckets-1.
-  static int HashExtension(const std::string& extension_id, uint32 client_key);
-
- private:
-  // Returns the profile for which extensions will be gathered.  Once a
-  // suitable profile has been found, future calls will continue to return the
-  // same value so that reported extensions are consistent.
-  Profile* GetMetricsProfile();
-
-  // The key used when hashing extension identifiers, derived from client_id.
-  const int client_key_;
-
-  // The profile for which extensions are gathered.  Once a profile is found
-  // its value is cached here so that GetMetricsProfile() can return a
-  // consistent value.
-  Profile* cached_profile_;
-
-  DISALLOW_COPY_AND_ASSIGN(HashedExtensionMetrics);
-};
-
-#endif  // CHROME_BROWSER_METRICS_EXTENSION_METRICS_H_