21372 Fix for issue flutter/#66502. (cla: yes, platform-web)

21383 E2e screenshot tests2 (cla: yes, platform-web)

21423 [web] Respond with null for unimplemented method channels (cla: yes, platform-web)

21438 Respect the –debug option in Firefox (cla: yes, platform-web, waiting for tree to go green)

21499 [web] Fix 3d transforms for html backend (cla: yes, platform-web)

21629 Add more TextStyle support to Paragraph in CanvasKit mode (cla: yes, platform-web)

21677 Pass angles for SweepGradient in degrees, not radians (cla: yes, platform-web)