
Added Element.dataset collection. While not strictly an Object it's
accessed like one.

R=arv
DELTA=10  (10 added, 0 deleted, 0 changed)


Revision created by MOE tool push_codebase.
MOE_MIGRATION=761101


olegshnitko/closure-compiler,ajukraine/closure-compiler,olegshnitko/closure-compiler,ajukraine/closure-compiler