A novelty. I am not sure how much Ding knew about the line, as he never said a word at the press  conference, but the move is logical and good.
1. d2d4  1... g8f6  2. g1f3  2... d7d5  3. c2c4  3... e7e6  4. b1c3  4... c7c6  5. e2e3  5... b8d7  6. f1d3  6... d5c4  7. d3c4  7... b7b5  8. c4d3  8... a7a6  9. e3e4  9... c6c5  10. e4e5  10... c5d4  11. c3b5  11... a6b5  12. e5f6  12... g7f6  13. e1g1  13... d8b6  14. d1e2 "The line was popular in the 1990s as well as in the match Anand-Kramnik, but  of course I did not remember anything..." (Navara) 14... b5b4  15. c1f4  The bishop often needs to get to g3 in order to defend the kingside. But  it might well be sacrificed in case Black pushes the e5 pawn prematurely. 15... h7h5 A surprise for White. The pawn intends to harrass the bishop. 16. f1c1  16... f8c5  17. a2a4 Looking for a way to reach the black king. 17... b4a3  18. b2a3  18... c8a6  19. a1b1  19... a6d3  20. e2d3 