[css-cascade] Fix the 'order of appearance' to talk only about declarations, as style attributes have no rules.

--HG--
extra : rebase_source : cd685a11ebe304f4ac2b9ed8e4239f5852a4b1fa
[css-cascade] Add to the Filtering Declarations step that a declaration must be syntactically valid.

--HG--
extra : rebase_source : f99cc001b1e04a8894bfa310d0b21f1b000f0a6c