Roll Dart SDK from 4c03f64b19f6 to 70577d6f2bba (1 revision) (#189031)

https://dart.googlesource.com/sdk.git/+log/4c03f64b19f6..70577d6f2bba

2026-07-06 dart-internal-merge@dart-ci-internal.iam.gserviceaccount.com
Version 3.13.0-275.0.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
Please CC codefu@google.com,dart-vm-team@google.com on the revert to
ensure that a human
is aware of the problem.

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

To report a problem with the AutoRoller itself, please file a bug:
https://issues.skia.org/issues/new?component=1389291&template=1850622

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

DEPS

diff --git a/DEPS b/DEPS
index 5b2ef2b..1cf2661 100644
--- a/DEPS
+++ b/DEPS
@@ -56,7 +56,7 @@
   # updated revision list of existing dependencies. You will need to
   # gclient sync before and after update deps to ensure all deps are updated.
   # updated revision list of existing dependencies.
-  'dart_revision': '4c03f64b19f6d0e72d3877f6e3d41406f40b72dd',
+  'dart_revision': '70577d6f2bba8cf9f4b357d10c217f5b4a61a13f',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py