The very first bits of resynthesizing elements from kernels.

pkg/front_end/lib/src/fasta/messages.dart

Index: pkg/front_end/lib/src/fasta/messages.dart
diff --git a/pkg/front_end/lib/src/fasta/messages.dart b/pkg/front_end/lib/src/fasta/messages.dart
index 72f2a09531509fd199417e874bed6d499a02fb49..2fb0dc0c29b8ee54347d411963999b67feb59e9e 100644
--- a/pkg/front_end/lib/src/fasta/messages.dart
+++ b/pkg/front_end/lib/src/fasta/messages.dart
@@ -12,7 +12,8 @@ import 'util/relativize.dart' show relativizeUri;
 
 import 'compiler_context.dart' show CompilerContext;
 
-import 'deprecated_problems.dart' show deprecated_InputError;
+import 'deprecated_problems.dart'
+    show deprecated_InputError, temporaryUntilPrintsRemovedEnablePrinting;
 
 import 'colors.dart' show cyan, magenta;
 
@@ -38,8 +39,10 @@ bool get setExitCodeOnProblem {
 
 void warning(Message message, int charOffset, Uri uri) {
   if (hideWarnings) return;
-  print(deprecated_format(
-      uri, charOffset, colorWarning("Warning: ${message.message}")));
+  if (temporaryUntilPrintsRemovedEnablePrinting) {
+    print(deprecated_format(
+        uri, charOffset, colorWarning("Warning: ${message.message}")));
+  }
   if (warningsAreFatal) {
     if (isVerbose) print(StackTrace.current);
     throw new deprecated_InputError(