Application: Use shared pointers

Fixes #1239

src/device/devicedatabasebackend.h

@@ -30,6 +30,7 @@
 #include <QList>
 #include <QString>
 
+#include "core/shared_ptr.h"
 #include "core/song.h"
 #include "core/musicstorage.h"
 
@@ -57,11 +58,11 @@ class DeviceDatabaseBackend : public QObject {
 
   static const int kDeviceSchemaVersion;
 
-  void Init(Database *db);
+  void Init(SharedPtr<Database> db);
   void Close();
   void ExitAsync();
 
-  Database *db() const { return db_; }
+  SharedPtr<Database> db() const { return db_; }
 
   DeviceList GetAllDevices();
   int AddDevice(const Device &device);
@@ -76,7 +77,7 @@ class DeviceDatabaseBackend : public QObject {
   void ExitFinished();
 
  private:
-  Database *db_;
+  SharedPtr<Database> db_;
   QThread *original_thread_;
 
 };