Roll Dart to 4126459. (flutter#4969)

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': '23ae4fa098a1c2011b72f5ad4d00383e1ac10a59',
+  'dart_revision': '41264590256de42c68de406fc180e338efc9420d',
 
   'dart_args_tag': '1.4.1',
   'dart_async_tag': '2.0.6',

travis/licenses_golden/licenses_third_party

@@ -1,4 +1,4 @@
-Signature: f15f70e4cdde38e61887aa34721faf73
+Signature: 51b000c3ae8a9d5678ad4183dbf86328
 
 UNUSED LICENSES:
 
@@ -6028,12 +6028,16 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 ====================================================================================================
 LIBRARY: dart
-ORIGIN: ../../../third_party/dart/runtime/vm/compiler/compiler_pass.cc + ../../../third_party/dart/LICENSE
+ORIGIN: ../../../third_party/dart/runtime/vm/compiler/backend/code_statistics.cc + ../../../third_party/dart/LICENSE
 TYPE: LicenseType.bsd
+FILE: ../../../third_party/dart/runtime/vm/compiler/backend/code_statistics.cc
+FILE: ../../../third_party/dart/runtime/vm/compiler/backend/code_statistics.h
 FILE: ../../../third_party/dart/runtime/vm/compiler/compiler_pass.cc
 FILE: ../../../third_party/dart/runtime/vm/compiler/compiler_pass.h
 FILE: ../../../third_party/dart/runtime/vm/datastream.cc
 FILE: ../../../third_party/dart/runtime/vm/finalizable_data.h
+FILE: ../../../third_party/dart/runtime/vm/type_testing_stubs.cc
+FILE: ../../../third_party/dart/runtime/vm/type_testing_stubs.h
 FILE: ../../../third_party/dart/sdk/lib/js/_js.dart
 FILE: ../../../third_party/dart/sdk/lib/js/_js_client.dart
 FILE: ../../../third_party/dart/sdk/lib/js/_js_server.dart