Make SmallStrings store an array of RefPtr<StringImpl>,
instead of a direct array of StringImpls.  This allows
us to remove a friend (and a layering violation) from
WTF::StringImpl, and makes it so that all StringImpls
are individually heap allocated.

* runtime/SmallStrings.cpp:
(JSC::SmallStringsStorage::rep):
(JSC::SmallStringsStorage::SmallStringsStorage):
* wtf/text/StringImpl.h:



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@58026 268f45cc-cd09-0410-ab3c-d52691b4dbfc