76102 improve the scrollbar behavior when viewport size changed (a: desktop, a: quality, cla: yes, f: scrolling, framework, platform-web, waiting for tree to go green)

76173 Scrollbar updates for native Android behavior (a: fidelity, cla: yes, f: material design, f: scrolling, framework, waiting for tree to go green)

76312 add keyboardDismissBehavior into SingleChildScrollView (cla: yes, f: scrolling, framework, waiting for tree to go green)

76739 Exposing ScrollBehaviors for app-wide settings (a: desktop, cla: yes, f: cupertino, f: material design, f: scrolling, framework, platform-web, severe: new feature, waiting for tree to go green)