Roll Dart SDK from 3a8c551 to 87b3768 (1 revision)

https://dart.googlesource.com/sdk.git/+log/3a8c551ec08e..87b37682b24f

2021-05-19 dart-luci-ci-builder@dart-ci.iam.gserviceaccount.com Version 2.14.0-129.0.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 dart-vm-team@google.com on the revert to ensure that a human
is aware of the problem.

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/master/autoroll/README.md

Author: skia-flutter-autoroll

DEPS

@@ -35,7 +35,7 @@ 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': '3a8c551ec08e821101cc9f6a368608f664339956',
+  'dart_revision': '87b37682b24f9edf11848f9cbadfd4a8b3a9ae03',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py