Correction.
Cruz never said he was against a contested convention.
In fact, he is planning on one.
He said he was against the other kind of convention.
Whatever the difference between the two is, this is what he said-
http://www.cbsnews.com/news/ted-cruz-beat-donald-trump-ballot-box-not-gop-convention/
that would be a brokered convention. Cruz is definitely on record being against it.
Cruz said that if you want to defeat Trump, you have to do it at the ballot box (as opposed to at Cleveland). The link to the interview in which he made that point has been posted again and again. Have you really never seen it?