upgrade Firefox to 83 (#22829)

lib/web_ui/dev/browser_lock.yaml

@@ -6,20 +6,31 @@
 ## version is 13.)
 ## Please refer to README's `Upgrade Browser Version` section for more details
 ## on how to update the version number.
-required_driver_version:
-  ## Make sure the major version of the binary in `browser_lock.yaml` is the
-  ## same for Chrome.
-  chrome: '84'
 chrome:
   # It seems Chrome can't always release from the same build for all operating
   # systems, so we specify per-OS build number.
   Linux: 768968 # Major version 84
   Mac: 768985 # Major version 84
   Win: 768975 # Major version 84
+required_driver_version:
+  ## Make sure the major version of the binary in `browser_lock.yaml` is the
+  ## same for Chrome.
+  chrome: '84'
+
+## Firefox does not use CIPD. To update the version, simply update it in this
+## file. However geckodriver does use CIPD. When upgrading geckodriver, update
+## it here, then follow the process in go/cipd-flutter-web (googlers only) to
+## create a new CIPD package.
 firefox:
-  version: '72.0'
+  version: '83.0'
+## geckodriver is used for testing Firefox Browser. It works with multiple
+## Firefox Browser versions.
+## See: https://github.com/mozilla/geckodriver/releases
+geckodriver: 'v0.28.0'
+
 edge:
   launcher_version: '1.2.0.0'
+
 ios-safari:
   # Make sure this version is the same version supported by LUCI macOS bots.
   # XCode on these bots will be updated once a year, do not forget to update
@@ -47,8 +58,3 @@ ios-safari:
   # This value will be differ depending on the phone.
   # For iOS 13.0 iPhone 11 Pro, this number is 1.15.
   scaleFactor: 1.00
-
-## geckodriver is used for testing Firefox Browser. It works with multiple
-## Firefox Browser versions.
-## See: https://github.com/mozilla/geckodriver/releases
-geckodriver: 'v0.26.0'