67557 enable null_check_on_nullable_type_parameter and tighten_type_of_initializing_formals (cla: yes, f: material design, framework, waiting for tree to go green)

67558 Some NNBD Test Conversion (cla: yes, f: material design, framework)

67562 [Material] Time picker semantics updates (a: accessibility, cla: yes, f: material design, framework)

67566 Revert “Wrap PopupMenu with SafeArea to respect status bar” (cla: yes, f: material design, framework)

67574 Implement documented behavior of WidgetsApp.builder (cla: yes, f: material design, framework, waiting for tree to go green)

67578 Re-land ‘Wrap PopupMenu with SafeArea to respect status bar’ (cla: yes, f: material design, framework, waiting for tree to go green)