The very first bits of resynthesizing elements from kernels.

pkg/front_end/lib/src/fasta/kernel/kernel_target.dart

Index: pkg/front_end/lib/src/fasta/kernel/kernel_target.dart
diff --git a/pkg/front_end/lib/src/fasta/kernel/kernel_target.dart b/pkg/front_end/lib/src/fasta/kernel/kernel_target.dart
index 3ca9a1fd9a9676ff7eed822b90572874221ea23c..96355ae5c0d08466b839e95efbed867f9ed1d9b9 100644
--- a/pkg/front_end/lib/src/fasta/kernel/kernel_target.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/kernel_target.dart
@@ -46,10 +46,11 @@ import '../compiler_context.dart' show CompilerContext;
 
 import '../deprecated_problems.dart'
     show
-        deprecated_formatUnexpected,
         deprecated_InputError,
+        deprecated_formatUnexpected,
         reportCrash,
-        resetCrashReporting;
+        resetCrashReporting,
+        temporaryUntilPrintsRemovedEnablePrinting;
 
 import '../dill/dill_target.dart' show DillTarget;
 
@@ -219,7 +220,9 @@ class KernelTarget extends TargetImplementation {
   void handleInputError(deprecated_InputError error, {bool isFullProgram}) {
     if (error != null) {
       String message = error.deprecated_format();
-      print(message);
+      if (temporaryUntilPrintsRemovedEnablePrinting) {
+        print(message);
+      }
       errors.add(message);
     }
     program = erroneousProgram(isFullProgram);
@@ -506,7 +509,8 @@ class KernelTarget extends TargetImplementation {
   Constructor makeDefaultConstructor() {
     return new Constructor(
         new FunctionNode(new EmptyStatement(), returnType: const VoidType()),
-        name: new Name(""));
+        name: new Name(""),
+        isSyntheticDefault: true);
   }
 
   void finishAllConstructors() {