Roll src/third_party/dart 5fbf7720f8..b6997deb3e (26 commits)

b6997deb3e Resolve typed constant initializers separately.
8053c43dde Compute static types for for-in loops
b9c87ebbda Add scanner languageVersionChanged callback
fa274ec059 Make each NullabilityNode track those nodes that are downstream of it.
407378879b Error reporting and ~no location data
8d4816b7ff Reimplement member usage tracking
b36734f4da Fix crash when duplicate fields have annotations
30e21f3dc0 Don't crash when additional exports contain duplicate names
9670b2ccb9 Update the server API to support context messages
58c6d78712 [vm] Check Zones are only [un]chained on the correct side of a safepoint transition.
4ce3aa7af1 [vm] Replace ^= assignments with = where possible
2e24a992c7 Support for 'nullabilitySuffix' in linked types.
481d6b9f30 Fix the windows bots
ee1192e693 [dart/vm] Extended graph checker
a32fee5d8e [dart/vm] GenericCheckBound (AOT) may throw
3b22a7ae46 [vm/profiler] Fix native stack walker to properly skip PC = 0xFF..FF
a30819a2f6 Add a diagnostic associated with the default List constructor
ac4fd50446 [vm, compiler] Check for length overflow when eliminating write barriers for variable-length objects.
7cb1365f7f replace individual scanner flags with scanner configuration
a20e7eee15 update scanner config based on language comment
26a82dbf38 Support for LibraryElemenet.entryPoint
de1966db11 Separately handle InterfaceType and FunctionType while collecting free type parameters.
e178b0726a [test] Speed up unicode-regexp-zero-length_test.
5896692b42 Introduce pkg/modular_test: a package to specify modular tests
d543d2e812 Check window.MediaSource before call constructor
46847f2239 Store super-invoked names for mixins.

DEPS

@@ -31,7 +31,7 @@ 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': '5fbf7720f8bcbf9723e50933f5b1c7d1bc940338',
+  'dart_revision': 'b6997deb3ea030145555195a295e599cf8099f40',
 
   # 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: 551e5f08ae5c955a071e7987f25566ae
+Signature: 3a6811f2d6af8b0c5cb5d3d2ef362d56
 
 UNUSED LICENSES:
 

sky/packages/sky_engine/LICENSE

@@ -3111,7 +3111,7 @@ dart
 Copyright (c) 2010, the Dart project authors.  Please see the AUTHORS file
 for details. All rights reserved.
 
- Redistribution and use in source and binary forms, with or without
+Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions are
 met:
     * Redistributions of source code must retain the above copyright