Roll src/third_party/dart 15a3bf8..ffefa12 (11 commits)

dart-lang/sdk@ffefa124a7 [vm] Initial support for bytecode generation in front-end server
dart-lang/sdk@daf0de7408 [vm/observatory] Update embedded version of catapult to catapult-project/catapult@8bd58eb.
dart-lang/sdk@f255c0c8d3 [vm/bytecode] Revise PushStatic bytecode instruction
dart-lang/sdk@f74b0ccfb8 Extract logic from DecoratedType.forElement into a new class, AlreadyMigratedCodeDecorator.
dart-lang/sdk@4ebde3fa9b [vm] Fix missing null check in FLAG_force_evacuation.
dart-lang/sdk@271ad96813 [cfe] Create Extension nodes for extensions
dart-lang/sdk@cd42e2b19a Make InstantiatedExtension a private class
dart-lang/sdk@0ee1633f40 Index references to extension methods.
dart-lang/sdk@38ca3819cc Don't include extended type into syntactic scope of extensions.
dart-lang/sdk@157336f7d6 Allow relative paths in update_static_error_tests.dart
dart-lang/sdk@d8f5970f0f [dart2js] prepare validator for k-limiting

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': '15a3bf82cbd67c2d73e9f6a46ec6a3e32d8229eb',
+  'dart_revision': 'ffefa124a77d76307eb41bbc4d7717aaa264e4f4',
 
   # 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: 72ff7af9d28bb2fdd1ca30b84a823cb3
+Signature: e4942a1a005fa1897a8f54eb29678b39
 
 UNUSED LICENSES: