Have AttributeSet::getRetAttributes() return an AttributeSet instead of Attribute.
Have AttributeSet::getRetAttributes() return an AttributeSet instead of Attribute.

This further restricts the use of the Attribute class to the Attribute family of
classes.


git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@173099 91177308-0d34-0410-b5e6-96231b3b80d8

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