7411 Dart SDK roll for 2019-01-08 (cla: yes)

7413 remove deprecated updateNode argument (cla: yes)

7414 Strut implementation (cla: yes)

7416 Dart SDK roll for 2019-01-08 (cla: yes)

7417 Dart SDK roll for 2019-01-09 (cla: yes)

7419 Dart SDK roll for 2019-01-09 (cla: yes)

7421 Dart SDK roll for 2019-01-09 (cla: yes)

7426 Refactor dynamic patching to use clearer naming and structure. (cla: yes)

7427 Allow embedders to add per shell idle notification callbacks. (cla: yes)