Oilpan: Prepare to move AbstractSQLTransactionBackend, SQLTransactionBackend, and SQLTransactionCoordinator::CoordinationInfo to Oilpan heap.

This CL changes the mapped type of m_coordinationInfoMap from copyable
object to OwnPtr<> or Member<>. So we need to update some code
in SQLTransactionCoordinator.

BUG=347902
R=ager@chromium.org, haraken@chromium.org

Review URL: https://codereview.chromium.org/198213005

git-svn-id: svn://svn.chromium.org/blink/trunk@169535 bbb929c8-8fbe-4397-9dbb-9b2b20218538