43657 Re-Land: Add focus nodes, hover, and shortcuts to switches, checkboxes, and radio buttons. (a: accessibility, cla: yes, f: material design, framework, team)

43658 Added note about design doc template. (cla: yes)

43662 Enable heroes_test.dart on the web matrix (cla: yes, framework, team, work in progress; do not review)

43667 Added a null check for ranges in the sourceReport map. (cla: yes, tool)

43669 Don’t read AndroidManifest.xml if it doesn’t exit (cla: yes, tool, waiting for tree to go green)

43674 Add missing import (cla: yes)

43675 Fix device lab tests (cla: yes)

43676 Allow multiple TimingsCallbacks (cla: yes, framework, severe: performance)