Oilpan: Prepare to move DatabaseContext to Oilpan heap.

Source/modules/webdatabase/DatabaseBackendBase.cpp

 /*
  * 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 232 matching lines @@
     // and hence we should also close it on that same thread. This means that the
     // SQLite database need to be closed by another mechanism (see
     // DatabaseContext::stopDatabases()). By the time we get here, the SQLite
     // database should have already been closed.
 
     ASSERT(!m_opened);
 }
 
 void DatabaseBackendBase::trace(Visitor* visitor)
 {
+    visitor->trace(m_databaseContext);
     visitor->trace(m_sqliteDatabase);
     visitor->trace(m_databaseAuthorizer);
 }
 
 void DatabaseBackendBase::closeDatabase()
 {
     if (!m_opened)
         return;
 
     m_sqliteDatabase.close();
@@ skipping 402 matching lines @@
 {
     executionContext()->addConsoleMessage(StorageMessageSource, ErrorMessageLevel, message);
 }
 
 ExecutionContext* DatabaseBackendBase::executionContext() const
 {
     return databaseContext()->executionContext();
 }
 
 } // namespace WebCore