[webcomponents] Ignore title attributes on style elements in shadow trees (#391)

Style elements inside a shadow tree should not be able to set the preferred stylesheet set for the document. Also, style elements inside a shadow tree should still be applied if it has a title element not matching the preferred stylesheet set of the top document.

https://lists.w3.org/Archives/Public/public-webapps/2015OctDec/0223.html


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Reply to this email directly or view it on GitHub:
https://github.com/w3c/webcomponents/issues/391