Add steps for crbug management to commit_checklist.md documentation

Add reminders to mark the crbug as "started" before starting
development work and to mark the crbug as "fixed" after landing the
CL.

Bug: None
Change-Id: Id79ff0843679c368773b10d22ea9d72e4b1691d2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1891730
Reviewed-by: Aga Wronska <[email protected]>
Commit-Queue: Toby Huang <[email protected]>
Cr-Commit-Position: refs/heads/master@{#711042}
diff --git a/docs/commit_checklist.md b/docs/commit_checklist.md
index 7e9fa367..992817f 100644
--- a/docs/commit_checklist.md
+++ b/docs/commit_checklist.md
@@ -20,6 +20,9 @@
 
     git checkout -b <branch_name> --track origin/master
 
+Mark the associated crbug as "started" so that other people know that you have
+started work on the bug. Doing this can avoid duplicated work.
+
 ## 2. Make your changes
 
 Do your thing. There's no further advice here about how to write or fix code.
@@ -140,8 +143,11 @@
 Click `Submit to CQ` to try your change in the commit queue (CQ), which will
 land it if successful.
 
+## 18. Cleanup
+
 After your CL is landed, you can use `git rebase-update` or `git cl archive` to
-clean up your local branches.
+clean up your local branches. These commands will automatically delete merged
+branches. Mark the associated crbug as "fixed".
 
 [//]: # (the reference link section should be alphabetically sorted)
 [contributing]: contributing.md