"Douglas refused to withdraw his dissent until Blackmun personally assured him that his position of declaring the abortion statutes unconstitutional was firm, and that he had no intention of reversing that position after reargument. Blackmun gave Douglas that assurance. . . . [A]s it turned out, Justice Douglas was the biggest winner of all. His prolonged tantrum had produced a firm commitment from Justice Blackmun to hold to his original position of voting to strike down the Texas and Georgia statutes."