Roll Dart SDK from 39179049ede9 to 51e3e9956f0f (1 revision) (#20702)

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': '39179049ede9c53826b8be7a8dbaf514d3d30a0d',
+  'dart_revision': '51e3e9956f0f0d6441e826e81247d89ea2019d79',
 
   # 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: 61adfb7bf27b234a6d23c59be5683d80
+Signature: 7f390e580421a174ef558e0ff9f07959
 
 UNUSED LICENSES: