Without doing a whole lot of research, I can say, quoting the Catholic Encyclopedia:
In the meantime, ambassadors from several Protestant princes and cities reached Trent. They made various demands, as: that the earlier decisions which were contrary to the Augsburg Confession should be recalled; that debates on questions in dispute between Catholics and Protestants should be deferred; that the subordination of the pope to an ecumenical council should be defined . . . .
That said, I would
love to know what people would say if there were a line in the documents of Vatican II that went, “Well, we were going to publish some statements about the Mass and the Eucharist, but we’d greatly prefer having the (name removed by moderator)ut of Protestants about it first before we say anything publicly. So we’re going to hold off for a while until any Protestant who wants to come can get here and prove all his ideas to us.” Can you even imagine what dark meaning people would ascribe to those words? Because that is
exactly what the Council of Trent said.
Needless to say, my point is not to run down the Council of Trent here, but to show vividly why the common practice – common in the case of Vatican II, that is – of drawing the wildest adverse inferences from any sort of openness or accommodation to the Protestants is so ill-conceived. If there were a line such as I gave above in the proceedings of Vatican II, there can be no doubt that it would be repeated
constantly as irrefutable “proof” that everything which came out of the Council was irretrievably tainted by a maniacal desire (they even
admitted it! 
) to please the Protestants, to become more Protestant, and so on and so forth. Yet obviously we do not think that in the case of the Council of Trent. This goes to show that arguments about what is “Protestant” have to be made on the basis of the facts, not of insinuations deriving from who was invited to what council.