63455 Fix SafeArea and SliverSafeArea debug flag properties (cla: yes, framework, waiting for tree to go green)

63461 Removed the inputFormatters from the text input fields used by the Date Pickers (f: material design, framework, waiting for tree to go green)

63495 migrate part of painting to nullsafety (framework, waiting for tree to go green)

63497 Add dispose to restoration example (d: api docs, d: examples, documentation, framework, waiting for tree to go green)

63502 Add native stacktrace field for PlatformException (cla: yes, framework)

63503 Update: Documentation for ListView constructor should warn about changing widget list (cla: yes, d: api docs, documentation, framework, waiting for tree to go green)

63515 allow null in compute for weak mode (cla: yes, framework, waiting for tree to go green)