15714 Roll src/third_party/dart c8f8c11b70b4..843bd2990881 (5 commits) (autoroller: commit, cla: yes)

15715 fix typo, update path metrics docs (cla: yes)

15736 Roll src/third_party/dart 843bd2990881..f96c48307d14 (10 commits) (autoroller: commit, cla: yes)

15737 Roll fuchsia/sdk/core/linux-amd64 from YPYqb… to MCe3R… (autoroller: commit, cla: yes)

15740 Fix Color API, move toCss to helper functions (cla: yes)