Roll src/third_party/dart f7902889b6..6e2b3f0326 (7 commits)

dart-lang/sdk@6e2b3f0326 [vm] Greatly reduce handle allocation during reload.
dart-lang/sdk@56b3dede78 Implement some missed methods for summary2 support
dart-lang/sdk@209c6f8ab9 [pkg:vm_service] fix some analysis errors in the generated vm_service library
dart-lang/sdk@b52b2c3910 [dart2js] Don't produce '-2' for default type argument values with new RTI.
dart-lang/sdk@f37fdef1c2 [vm, service] Fix out-of-bounds access when processing requestHeapSnapshot's arguments.
dart-lang/sdk@5087b99361 Report final re-assignment in for-in parts. Fixes #30486
dart-lang/sdk@0ad703b534 [pkg:vm_service] re-generate the library based on the latest spec

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': 'f7902889b6e30a8b9d71416e1facf3c509aad06f',
+  'dart_revision': '6e2b3f0326bc15ad938319cbbb151f183d064609',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py

ci/licenses_golden/licenses_third_party

-Signature: 8150fbd17d2122e7cb6fe8fcfb41d8d5
+Signature: 5b79ad77f8b89f4b9c8c5a94fca653cb
 
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