Roll Dart SDK from 21f2997a8fc6 to 6334e84d6956 (4 revisions) (flutter#38187)

https://dart.googlesource.com/sdk.git/+log/21f2997a8fc6..6334e84d6956

2022-12-10 [email protected] Version 3.0.0-16.0.dev
2022-12-10 [email protected] Version 3.0.0-15.0.dev
2022-12-09 [email protected] Version 3.0.0-14.0.dev
2022-12-09 [email protected] Version 3.0.0-13.0.dev

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/dart-sdk-flutter-engine
Please CC [email protected],[email protected],[email protected] on the revert to ensure that a human
is aware of the problem.

To file a bug in Flutter Engine: https://github.com/flutter/flutter/issues/new/choose

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md

Author: skia-flutter-autoroll

DEPS

@@ -48,7 +48,7 @@ vars = {
   # Dart is: https://github.com/dart-lang/sdk/blob/main/DEPS
   # You can use //tools/dart/create_updated_flutter_deps.py to produce
   # updated revision list of existing dependencies.
-  'dart_revision': '21f2997a8fc68a791f9bae48ef3f429fd483cc54',
+  'dart_revision': '6334e84d695669af25587ae265ccbb92e2cd3982',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py
@@ -57,7 +57,7 @@ vars = {
   'dart_boringssl_rev': '87f316d7748268eb56f2dc147bd593254ae93198',
   'dart_browser_launcher_rev': '5fa0bd6cddc33785f43c920576fc03dcee1c3caa',
   'dart_clock_rev': '8a8231fa7912d84c7e99236b7800cfbef5ea7ae5',
-  'dart_collection_rev': 'caf6802bbea65a1a2f9c455add31449dc15b92ba',
+  'dart_collection_rev': 'cdb11d410b67279d81673def5a8a78dfc0dec2eb',
   'dart_devtools_rev': 'dd3fade2bd2ef74fc6102e56333a48f0efc594d3',
   'dart_protobuf_rev': '2706b53d2175b5e1081603059ef1b7b30956f6b8',
   'dart_pub_rev': '21aa23f148a428ae4dd97a27ecc70b08c1328089',

ci/licenses_golden/licenses_third_party

@@ -1,4 +1,4 @@
-Signature: bbed4848080f583e902b9c35c163678b
+Signature: 881061516b2af2828505da1bd8d7f8e0
 
 UNUSED LICENSES: