Oilpan: insist that CompositeCreators be stack allocated.

And add missing Oilpan (transition) type to the heap allocated
MessagePortArray member of Deserializer.

R=haraken@chromium.org
BUG=340522

Review URL: https://codereview.chromium.org/362923003

git-svn-id: svn://svn.chromium.org/blink/trunk@177375 bbb929c8-8fbe-4397-9dbb-9b2b20218538