Roll Dart to 4cf2d39 (flutter#6332)

Included CLs:

4cf2d39 [VM runtime] Store Smi instance type in type test cache when using the interpreter.
a6b1a99 Make mixins abstract by default
ab305f2 Recover from duplicated declarations
4e32a35 Ignore synthetic elements created by the parser
fc04f56 [infra] Remove deleted Dart 1 builders (app/precomp) from the test matrix
8477dc2 Update status after 570fd5a
1652850 Compute static types during impact computation
b4341f0 Remove unneeded method rti need
570fd5a Error on re-export, export and import of libraries with same name.
4b312b2 Support multiple superclasses in the mixin `on` clause.
8debb4e [fuchsia] Add zx_vmo_replace_as_executable calls
d34337a Ignore noSuchMethod() for the purpose of searching concrete member implementations.
b6284b4 Revert "[VM] Dart_Initialize no longer crashes after Dart_Cleanup"
94481ad [vm] Only include debugger/profiler slots in RawCode in product mode.
519ee90 [VM] Dart_Initialize no longer crashes after Dart_Cleanup
5349754 [vm] Specialize 'new List()' on kernel AST
afd4cc9 [vm/tfa] Infer concrete class of int literals in TFA
a4d48f4 [vm/tfa] Infer concrete class of string literals in TFA
9106228 [vm, dwarf] Set default_is_stmt to true for compatability with dsymutil.
6ce0dc0 dartfix stub implementation
e4eb243 Look into superclassConstraints while searching for a member in interfaces.
95d37b0 Revert "Implement inheritance/override checks from the spec."
355c73d [VM] Remove support for option --no-preview-dart-2
95b8a19 Mixin declarations don't have supertype, fix isMoreSpecificThan().
e9586a5 [vm] Update workaround for Android Kernel bug (b089d4f).
ef7d144 Add regression test for issue 34392.
56f6c52 large_class_declaration_test is slow now.
0ac3b8f [fuchsia] Add missing vm:entry-point annotation
19e844e [dart/fuzzing] Use current directory as SDK top (by default)
58e44c1 Don't use ClassElementImpl for now in override checking.
62d154f [vm/bytecode] Record null-initialized fields in bytecode
70cc34d Custom format errors and exceptions to show traces
9583113 Fix NPE when accessing superclass
836a1d7 Implement inheritance/override checks from the spec.
d070397 Remove redundant resolution
dba8b37 [vm] Benchmark for reading kernel bytecode

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': 'a2eb050044eec93f0844667b8b6132e858467e4e',
+  'dart_revision': '4cf2d3990bac1f1df2f524899e1560a3683f3133',
 
   'dart_args_tag': '1.4.4',
   'dart_async_tag': '2.0.8',

ci/licenses_golden/licenses_third_party

@@ -1,4 +1,4 @@
-Signature: 560e6d4446f2dc19f142baa51148b61a
+Signature: 55639f553e457f899c0862a7c92d7676
 
 UNUSED LICENSES: