72207 Fix navigator 2.0 in Flutter Web (cla: yes, framework, waiting for tree to go green)

72295 Add text to –analyze-size command output to launch DevTools with size data (cla: yes, tool)

72297 Migrate some material doc samples to null safety. (cla: yes, f: material design, framework, waiting for tree to go green)

72300 Fixed issue for SliverAppBar collapsedHeight (cla: yes, f: material design, f: scrolling, framework, waiting for tree to go green)

72303 Migrate some more material doc samples to null safety. (cla: yes, f: material design, framework, waiting for tree to go green)