[dart2js,ddc] Enable late lowering in dart2js and ddc

Change-Id: I77d99bade4bf0e094f04f222743c5fec19495851
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/126101
Commit-Queue: Johnni Winther <[email protected]>
Reviewed-by: Nicholas Shahan <[email protected]>
Reviewed-by: Sigmund Cherem <[email protected]>

Author: johnniwinther

pkg/compiler/lib/src/kernel/dart2js_target.dart

@@ -53,10 +53,8 @@ class Dart2jsTarget extends Target {
   @override
   bool get enableNoSuchMethodForwarders => true;
 
-  // TODO(johnniwinther): Change this to `false` when late field lowering is
-  // ready.
   @override
-  bool get supportsLateFields => true;
+  bool get supportsLateFields => false;
 
   @override
   List<String> get extraRequiredLibraries => _requiredLibraries[name];

pkg/dev_compiler/lib/src/kernel/target.dart

@@ -23,10 +23,8 @@ class DevCompilerTarget extends Target {
   @override
   bool get enableSuperMixins => true;
 
-  // TODO(johnniwinther): Change this to `false` when late field lowering is
-  // ready.
   @override
-  bool get supportsLateFields => true;
+  bool get supportsLateFields => false;
 
   @override
   String get name => 'dartdevc';