3545 Honor, and scrub, the 1.0 compatibility promise (cla: yes, p: android_intent, p: connectivity, p: device_info, p: package_info, p: path_provider, p: sensors, p: share, p: shared_preferences, p: url_launcher, p: video_player, platform-linux, platform-macos, platform-web, platform-windows)

3550 [file_selector_web] Migrated to null-safety (cla: yes, nnbd, p: file_selector, platform-web)

3554 [file_selector_web] update documentation #76067 (cla: yes, p: file_selector, platform-web)

3561 [video_player] Ignore setting mixWithOthers in web (cla: yes, p: video_player, platform-web)