89073 Prevent exceptions in _describeRelevantUserCode from hiding other exceptions (framework, cla: yes, waiting for tree to go green)

89076 Add all cubics to Cubic class doc (framework, cla: yes, d: api docs, d: examples, waiting for tree to go green, documentation)

89079 Add & improve DropdownButtonFormField reference to DropdownButton (framework, f: material design, cla: yes, d: api docs, waiting for tree to go green, documentation)

89081 Add gems to framework_tests_misc Mac dependencies to get cocoapods (cla: yes, waiting for tree to go green)

89084 Roll Engine from 497533a8abbe to 97240692e5e0 (2 revisions) (cla: yes, waiting for tree to go green)