Oilpan: Prepare to move DatabaseContext to Oilpan heap.

Source/modules/webdatabase/DatabaseBackendBase.h

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  * Copyright (C) 2013 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 104 matching lines @@
     void reportOpenDatabaseResult(int errorSite, int webSqlErrorCode, int sqliteErrorCode);
     void reportChangeVersionResult(int errorSite, int webSqlErrorCode, int sqliteErrorCode);
     void reportStartTransactionResult(int errorSite, int webSqlErrorCode, int sqliteErrorCode);
     void reportCommitTransactionResult(int errorSite, int webSqlErrorCode, int sqliteErrorCode);
     void reportExecuteStatementResult(int errorSite, int webSqlErrorCode, int sqliteErrorCode);
     void reportVacuumDatabaseResult(int sqliteErrorCode);
     void logErrorMessage(const String&);
     static const char* databaseInfoTableName();
 
     RefPtr<SecurityOrigin> m_contextThreadSecurityOrigin;
-    RefPtr<DatabaseContext> m_databaseContext; // Associated with m_executionContext.
+    RefPtrWillBeMember<DatabaseContext> m_databaseContext; // Associated with m_executionContext.
 
     String m_name;
     String m_expectedVersion;
     String m_displayName;
     unsigned long m_estimatedSize;
     String m_filename;
 
     DatabaseBase* m_frontend;
 
 #if !LOG_DISABLED || !ERROR_DISABLED
     String databaseDebugName() const { return m_contextThreadSecurityOrigin->toString() + "::" + m_name; }
 #endif
 
 private:
     DatabaseGuid m_guid;
     bool m_opened;
     bool m_new;
     const bool m_isSyncDatabase;
 
     SQLiteDatabase m_sqliteDatabase;
 
     RefPtrWillBeMember<DatabaseAuthorizer> m_databaseAuthorizer;
 
     friend class DatabaseServer;
 };
 
 } // namespace WebCore
 
 #endif // DatabaseBackendBase_h