28749 Add minimum time gap requirement to double tap (cla: yes, f: gestures, framework)

28751 Expose decorationThickness in TextStyle. Roll engine (12 commits) (a: typography, cla: yes, framework)

28752 FAB Snippet for API Docs (cla: yes, d: api docs, d: examples, f: material design, framework)

28756 Handle Cupertino back gesture interrupted by Navigator push (cla: yes, f: cupertino, framework)

28759 switch tool tests to build runner (cla: yes)

28799 Add semantics label to FadeInImage. (cla: yes, framework)

28809 fix some formatting issues (cla: yes, framework, team)