Roll Dart SDK from 3ec7f1f92216 to 7642080abaf7 (2 revisions) (flutter#39702)

https://dart.googlesource.com/sdk.git/+log/3ec7f1f92216..7642080abaf7

2023-02-16 [email protected] Version 3.0.0-247.0.dev
2023-02-16 [email protected] Version 3.0.0-246.0.dev

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/dart-sdk-flutter-engine
Please CC [email protected],[email protected],[email protected],[email protected] on the revert to ensure that a human
is aware of the problem.

To file a bug in Flutter Engine: https://github.com/flutter/flutter/issues/new/choose

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md

Author: skia-flutter-autoroll

DEPS

@@ -48,7 +48,7 @@ vars = {
   # Dart is: https://github.com/dart-lang/sdk/blob/main/DEPS
   # You can use //tools/dart/create_updated_flutter_deps.py to produce
   # updated revision list of existing dependencies.
-  'dart_revision': '3ec7f1f922160727ba6e5b0989e3fea555eb5d82',
+  'dart_revision': '7642080abaf7c69758fb7726e75a523d7597902a',
 
   # 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: 5cf9493e2cab0d3aa50d13ccc411a98f
+Signature: 57d971e6aef1c537cd5807cbc59e6cdd
 
 ====================================================================================================
 LIBRARY: angle