69781 Added dartpad examples for SliverAppBar (adopt a widget, cla: yes, d: api docs, d: examples, documentation, f: material design, framework, team, waiting for tree to go green)

69783 Reduce refresh indicator pull-down distance (cla: yes, f: material design, framework)

69793 Do not crash if RichText has recognizers without handlers (cla: yes, framework, waiting for tree to go green)

69795 Default Keyboard ScrollActions with PrimaryScrollController (a: desktop, cla: yes, f: cupertino, f: focus, f: material design, f: scrolling, framework, platform-web, severe: new feature, waiting for tree to go green)

69799 Choose higher-res image variants on low-DPR screens (cla: yes, framework)