Adds a notion of private symbols, mainly intended for internal use, especially, self-hosting of built-in types that would otherwise require new C++ classes.
On the JS side (i.e., in built-ins), private properties can be created and accessed through a set of macros:
NEW_PRIVATE(print_name)
HAS_PRIVATE(obj, sym)
GET_PRIVATE(obj, sym)
SET_PRIVATE(obj, sym, val)
DELETE_PRIVATE(obj, sym)
In the V8 API, they are accessible via a new class Private, and respective HasPrivate/Get/Private/SetPrivate/DeletePrivate methods on calss Object.
These APIs are designed and restricted such that their implementation can later be replaced by whatever ES7+ will officially provide.
R=yangguo@chromium.org
BUG=
Review URL: https://codereview.chromium.org/48923002
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@17683 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
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