Cops don't make arrests typically if they know there won't be any charges brought. You must think Texas, the state and its law apparatus, has infinite resources to prosecute low level marijuana users within the city limits of one of the state's largest urban areas. Newsflash; they don't, and won't.
Abortion is literally a hundred times more important to the state than weed is, sorry jabroni.
They can easily arrest someone, what you're talking about is if they will prosecute.