Roll src/third_party/dart 0506882b37..6bf1f8e280 (9 commits)

dart-lang/sdk@6bf1f8e280 [vm] Fix WriteByteSequence for simarm_x64
dart-lang/sdk@b4e66ed3d0 Add highlighting for extensions
dart-lang/sdk@fcc99f1e06 [dart2js] new-rti: naming of interface type parameters
dart-lang/sdk@f450cf399e [vm/bytecode] Add UncheckedClosureCall instruction
dart-lang/sdk@8dc4148516 Add await to all assertErrors/assertNoErrorsInCode tests.
dart-lang/sdk@8e17249b62 Refactor Flutter property tests.
dart-lang/sdk@7de08740f2 Infer types of fields and field formal parameters together.
dart-lang/sdk@9d204ca5d8 Start adding 'Container' properties.
dart-lang/sdk@1865a3c911 Produce diagnostic when extension override argument is not assignable to the extended type

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': '0506882b3795833959cda7feb80b3b22dab88068',
+  'dart_revision': '6bf1f8e280f29eee422c3c45a288f4100448f0cc',
 
   # 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

@@ -1,4 +1,4 @@
-Signature: 081199c4ccd521b162ab7fc2ee0f113d
+Signature: 52bdc7348e1d160fcea1dc48ae16b3c6
 
 UNUSED LICENSES: