Move code for instantiating Invocation to Target.

pkg/front_end/lib/src/fasta/dill/dill_target.dart

Index: pkg/front_end/lib/src/fasta/dill/dill_target.dart
diff --git a/pkg/front_end/lib/src/fasta/dill/dill_target.dart b/pkg/front_end/lib/src/fasta/dill/dill_target.dart
index 9a51575c051ee82b4f261834ee764fe4d4acc299..858264fc7fbdd77642446d0b681e773122c1ac01 100644
--- a/pkg/front_end/lib/src/fasta/dill/dill_target.dart
+++ b/pkg/front_end/lib/src/fasta/dill/dill_target.dart
@@ -8,6 +8,8 @@ import 'dart:async' show Future;
 
 import 'package:kernel/ast.dart' show Class;
 
+import 'package:kernel/target/targets.dart' show getTarget;
+
 import '../errors.dart' show internalError;
 import '../kernel/kernel_builder.dart' show ClassBuilder;
 import '../target_implementation.dart' show TargetImplementation;
@@ -20,8 +22,9 @@ class DillTarget extends TargetImplementation {
   bool isLoaded = false;
   DillLoader loader;
 
-  DillTarget(Ticker ticker, TranslateUri uriTranslator)
-      : super(ticker, uriTranslator) {
+  DillTarget(
+      Ticker ticker, TranslateUri uriTranslator, String backendTargetName)
+      : super(ticker, uriTranslator, getTarget(backendTargetName, null)) {
     loader = new DillLoader(this);
   }