Installer support for Windows 10 inactive user toast.

chrome/installer/util/experiment_storage.h

 // Copyright 2017 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_INSTALLER_UTIL_EXPERIMENT_STORAGE_H_
 #define CHROME_INSTALLER_UTIL_EXPERIMENT_STORAGE_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "base/strings/string16.h"
 #include "base/win/scoped_handle.h"
 
 namespace installer {
 
 class Experiment;
 struct ExperimentMetrics;
 
 // Manages the storage of experiment state on the machine.
 //
-// Participation is a per-install property evaluated one time to determine
-// whether or not the install as a whole participates in the study. It is
-// stored in the install's ClientState key.
+// Participation is a per-install property evaluated one time to determine which
+// study the client participates in. It is stored in the install's ClientState
+// key.
 //
 // ExperimentMetrics are stored in a per-install experiment_label, while the
 // fine-grained Experiment data are stored in a per-user key in Chrome's
 // ClientState or ClientStateMedium key. For system-level installs, metrics are
 // reported for only a single user on the machine, so only that one user will
 // participate in the experiment.
 //
 // Owing to this "metrics are per-install" property in the face of potentially
 // multiple users running the same install, ExperimentMetrics are considered the
 // source of truth for an install's participation in the experiment. For any
 // given state expressed in the experiment_label holding these metrics, there
 // should be matching Experiment data for precisely one user.
 //
 // As state is written across multiple locations in the registry, a global
 // mutex is used for all reads and writes to ensure consistent state.
 class ExperimentStorage {
  public:
-  enum class Participation {
-    // No participation state was found for the install.
-    kNotEvaluated,
+  // An identifier of which study the install participates in.
+  using Study = uint32_t;
 
-    // The client is not participating in the study.
-    kNotParticipating,
-
-    // The client is participating in the study.
-    kIsParticipating,
-  };
+  // The possible Study values.
+  static constexpr Study kNoStudySelected = 0;
+  static constexpr Study kStudyOne = 1;
+  static constexpr Study kStudyTwo = 2;
 
   // Grants the holder exclusive access to the data in the registry. Consumers
   // are expected to not hold an instance across any blocking operations.
   class Lock {
    public:
     ~Lock();
 
     // Reads the participation state for the install. Returns false in case of
-    // error.
-    bool ReadParticipation(Participation* participation);
+    // error. |participation| is set to kNotEvaluated if no value is present;
+    // otherwise, it is set to the value found.
+    bool ReadParticipation(Study* participation);
 
     // Writes the participation state for the install. Returns false if the
     // write failed.
-    bool WriteParticipation(Participation participation);
+    bool WriteParticipation(Study participation);
 
     // Loads the experiment metrics and data from the registry. Returns false if
     // the state in the registry corresponds to a different user or could not be
     // read.
     bool LoadExperiment(Experiment* experiment);
 
     // Stores the experiment metrics and data in |experiment| into the registry.
     bool StoreExperiment(const Experiment& experiment);
 
     // Loads per-install experiment metrics into |metrics|. Returns true if a
@@ skipping 62 matching lines @@
 
   // A global mutex with a distinct name for the current installation.
   base::win::ScopedHandle mutex_;
 
   DISALLOW_COPY_AND_ASSIGN(ExperimentStorage);
 };
 
 }  // namespace installer
 
 #endif  // CHROME_INSTALLER_UTIL_EXPERIMENT_STORAGE_H_