DatabaseContext needs to outlive the ScriptExecutionContext.
https://bugs.webkit.org/show_bug.cgi?id=108355.

Reviewed by Geoffrey Garen.

Added a RefPtr<DatabaseContext> in ScriptExecutionContext to keep the
DatabaseContext alive until after ScriptExecutionContext destructs.

No new tests.

* Modules/webdatabase/DatabaseContext.cpp:
(WebCore::DatabaseContext::DatabaseContext):
* dom/ScriptExecutionContext.cpp:
(WebCore::ScriptExecutionContext::setDatabaseContext):
* dom/ScriptExecutionContext.h:
(ScriptExecutionContext):



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@141431 268f45cc-cd09-0410-ab3c-d52691b4dbfc