Cherrypick the Dart roll to unblock the internal roll (#29920)

* Roll Dart SDK from 7d957c006c4f to 91e3fa160432 (2 revisions) (#29803)

* Update ci.yaml to enable the tests

Co-authored-by: skia-flutter-autoroll <skia-flutter-autoroll@skia.org>
diff --git a/.ci.yaml b/.ci.yaml
index 12abdde..4409b0d 100644
--- a/.ci.yaml
+++ b/.ci.yaml
@@ -11,6 +11,7 @@
   - dev
   - beta
   - stable
+  - flutter-2.8-candidate.8
 
 platform_properties:
   linux:
diff --git a/DEPS b/DEPS
index 3e35448..495e5c8 100644
--- a/DEPS
+++ b/DEPS
@@ -39,7 +39,7 @@
   # 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': '7d957c006c4f7ce18752de791ecba32d0e7e398f',
+  'dart_revision': '91e3fa1604328542b8b81c77753af04b90d3a788',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py
diff --git a/ci/licenses_golden/licenses_third_party b/ci/licenses_golden/licenses_third_party
index d724835..47f7c61 100644
--- a/ci/licenses_golden/licenses_third_party
+++ b/ci/licenses_golden/licenses_third_party
@@ -1,4 +1,4 @@
-Signature: e94985c18fe1aa8ef57edf44946a7c57
+Signature: fc54f271ff2fc1a2dd860c34464f5f7c
 
 UNUSED LICENSES: