* Manual roll of Dart from 24c7666def...40fd1c456e

dart-lang/sdk@40fd1c456e Revert "[dart:io] Add Abort() on HttpClientRequest"
dart-lang/sdk@17d7296a42 [vm/nnbd/bytecode] Fix reuse of type arguments in bytecode
dart-lang/sdk@58b6f40c73 Issue 42797. Understand in legacy libraries that a function returning Never (in Null Safety library) never returns. (reland)
dart-lang/sdk@fc8a6d9f9b [VM/compiler] Dereference TypeRef literal when propagating constants.
dart-lang/sdk@0689ec527a Move "test.dart" (well, most of its contents) into pkg/test_runner.
dart-lang/sdk@1094b3c61d Prepare static error test updater tool to handle web tests.
dart-lang/sdk@b258585f2f [observatory] Migrate from deprecated isInstanceOf to isA.
dart-lang/sdk@dfe1d9b682 Disable OverrideContributor for Cider.
dart-lang/sdk@aea99b2f5c scope debug property assist to Diagnosticables
dart-lang/sdk@4b96f20a79 [dart:io] Add Abort() on HttpClientRequest
dart-lang/sdk@1b1a39708c [build] Use frameworks instead of libs
dart-lang/sdk@3fef522496 Revert "Reland "[vm] Replaces fuchsia.deprecatedtimezone""
dart-lang/sdk@8c664d4f3f Revert "Issue 42797. Understand in legacy libraries that a function returning Never (in Null Safety library) never returns."
dart-lang/sdk@2efb5bebc7 [ dart:_http ] Fix typo in HTTP response timeline event
dart-lang/sdk@0884dae36c Revert "Fix the #include path for ICU headers"
dart-lang/sdk@5171534e81 Scope tweaks. Report REFERENCED_BEFORE_DECLARATION in more places.
dart-lang/sdk@6bba75079a Issue 42797. Understand in legacy libraries that a function returning Never (in Null Safety library) never returns.
dart-lang/sdk@b4ebbb7f5c [build] Update gn to match Fuchsia
dart-lang/sdk@cb428a7a02 [dart2js] Remove old bug work around in collector.
dart-lang/sdk@08663c20ab Change flutter patch to match existing DEPS on master branch
dart-lang/sdk@146ad014d9 update js/meta for the 2.10 dev sdk
dart-lang/sdk@488c718793 [co19] Roll co19 to d79951e06e443213243e54c2c32694b79a221b65
dart-lang/sdk@ba20edd7be Add patch for flutter-engine when changing to version 2.10

* Rev buildroot to latest version.

* Update license.

* update.

* Update gn revision.

* Format BUILD.gn files as the gn revision has been updated.