Roll Dart SDK from 5acb5fc to a9d5833 (4 revisions)

https://dart.googlesource.com/sdk.git/+log/5acb5fcf84cb..a9d583383410

2020-11-02 dart-luci-ci-builder@dart-ci.iam.gserviceaccount.com Version 2.12.0-12.0.dev
2020-11-02 dart-luci-ci-builder@dart-ci.iam.gserviceaccount.com Version 2.12.0-11.0.dev
2020-11-02 dart-luci-ci-builder@dart-ci.iam.gserviceaccount.com Version 2.12.0-10.0.dev
2020-11-01 dart-luci-ci-builder@dart-ci.iam.gserviceaccount.com Version 2.12.0-9.0.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 dart-vm-team@google.com on the revert to ensure that a human
is aware of the problem.

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/master/autoroll/README.md

Author: skia-flutter-autoroll

DEPS

@@ -34,7 +34,7 @@ vars = {
   # Dart is: https://github.com/dart-lang/sdk/blob/master/DEPS.
   # You can use //tools/dart/create_updated_flutter_deps.py to produce
   # updated revision list of existing dependencies.
-  'dart_revision': '5acb5fcf84cb097468d77208ae5cf5b743ab76d8',
+  'dart_revision': 'a9d5833834109773eb0186242d3dd9a778807d83',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py
@@ -43,11 +43,11 @@ vars = {
   'dart_boringssl_rev': '4dfd5af70191b068aebe567b8e29ce108cee85ce',
   'dart_clock_rev': 'a494269254ba978e7ef8f192c5f7fec3fc05b9d3',
   'dart_collection_rev': 'e4bb038ce2d8e66fb15818aa40685c68d53692ab',
-  'dart_dart_style_tag': '1.3.8',
+  'dart_dart_style_tag': '1.3.8+1',
   'dart_http_retry_tag': '0.1.1',
   'dart_http_throttle_tag': '1.0.2',
   'dart_intl_tag': '0.17.0-nullsafety',
-  'dart_linter_tag': '0.1.121',
+  'dart_linter_tag': '0.1.122',
   'dart_oauth2_tag': '1.6.0',
   'dart_protobuf_rev': '3746c8fd3f2b0147623a8e3db89c3ff4330de760',
   'dart_pub_rev': '5b4df5a6f931c63622ac349602d6ef0367e8070f',

ci/licenses_golden/licenses_third_party

@@ -1,4 +1,4 @@
-Signature: 41941fb8ed759d1965409d6797c6a61d
+Signature: c55e82fda8f939e4cdbeb9c2c004e7d9
 
 UNUSED LICENSES: