10656 fix iOS keyboard crash : -[__NSCFString substringWithRange:], range o… (cla: yes)

10662 bump local podspec’s ios deployment target version from 7.0 to 8.0 (cla: yes)

10663 Roll src/third_party/dart 8cd01287b4..574c4a51c6 (35 commits) (cla: yes)

10667 Roll buildroot for ANGLE support (cla: yes)

10671 Roll src/third_party/dart 574c4a51c6..c262cbd414 (11 commits) (cla: yes)

10674 When setting up AOT snapshots from symbol references, make buffer sizes optional. (cla: yes)

10675 Improvements to the flutter GDB script (cla: yes)