Extract kArcEnabled preference from ArcSessionManager part 2.

chrome/browser/chromeos/arc/arc_play_store_enabled_preference_handler.h

Index: chrome/browser/chromeos/arc/arc_play_store_enabled_preference_handler.h
diff --git a/chrome/browser/chromeos/arc/arc_play_store_enabled_preference_handler.h b/chrome/browser/chromeos/arc/arc_play_store_enabled_preference_handler.h
new file mode 100644
index 0000000000000000000000000000000000000000..0847714756af7818ac6e36b0a333857e0f74ff03
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+++ b/chrome/browser/chromeos/arc/arc_play_store_enabled_preference_handler.h
@@ -0,0 +1,63 @@
+// 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_BROWSER_CHROMEOS_ARC_ARC_PLAY_STORE_ENABLED_PREFERENCE_HANDLER_H_
+#define CHROME_BROWSER_CHROMEOS_ARC_ARC_PLAY_STORE_ENABLED_PREFERENCE_HANDLER_H_
+
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+#include "components/prefs/pref_change_registrar.h"
+#include "components/sync_preferences/pref_service_syncable_observer.h"
+
+class Profile;
+
+namespace arc {
+
+class ArcSessionManager;
+
+// Observes Google Play Store enabled preference (whose key is "arc.enabled"
+// for historical reason), and controls ARC via ArcSessionManager.
+// In addition, this controls showing/hiding a notification to enable Google
+// Play Store.
+class ArcPlayStoreEnabledPreferenceHandler
+    : public sync_preferences::PrefServiceSyncableObserver {
+ public:
+  ArcPlayStoreEnabledPreferenceHandler(Profile* profile,
+                                       ArcSessionManager* arc_session_manager);
+  ~ArcPlayStoreEnabledPreferenceHandler() override;
+
+  // Starts observing Google Play Store enabled preference change.
+  // Also, based on its initial value, this may start ArcSession, or may start
+  // removing the data, as initial state.
+  // In addition, this triggers to show ArcAuthNotification, if necessary.
+  void Start();
+
+ private:
+  // Called when Google Play Store enabled preference is changed.
+  void OnPreferenceChanged();
+
+  // Updates enabling/disabling of ArcSessionManager. Also, sets
+  // ArcSupportHost's managed state.
+  void UpdateArcSessionManager();
+
+  // sync_preferences::PrefServiceSyncableObserver:
+  void OnIsSyncingChanged() override;
+
+  Profile* const profile_;
+
+  // Owned by ArcServiceLauncher.
+  ArcSessionManager* const arc_session_manager_;
+
+  // Registrar used to monitor ARC enabled state.
+  PrefChangeRegistrar pref_change_registrar_;
+
+  // Must be the last member.
+  base::WeakPtrFactory<ArcPlayStoreEnabledPreferenceHandler> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(ArcPlayStoreEnabledPreferenceHandler);
+};
+
+}  // namespace arc
+
+#endif  // CHROME_BROWSER_CHROMEOS_ARC_ARC_PLAY_STORE_ENABLED_PREFERENCE_HANDLER_H_