The very first bits of resynthesizing elements from kernels.

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

Index: pkg/front_end/lib/src/fasta/deprecated_problems.dart
diff --git a/pkg/front_end/lib/src/fasta/deprecated_problems.dart b/pkg/front_end/lib/src/fasta/deprecated_problems.dart
index 90897d9eeae9ec76da1194649b12facc80bcceed..00ab3370569f2ab25e060f30c5bca8a5ec37f6ff 100644
--- a/pkg/front_end/lib/src/fasta/deprecated_problems.dart
+++ b/pkg/front_end/lib/src/fasta/deprecated_problems.dart
@@ -26,6 +26,13 @@ bool hasCrashed = false;
 /// [resetCrashReporting].
 Uri firstSourceUri;
 
+/// This flag is a temporary solution for preventing printing a lot
+/// of information on the console. Analyzer starts using Fasta to generate
+/// kernels to resynthesize its element models from it. We don't want to
+/// see all these errors and warnings on the console, while running test or
+/// in production. TODO(scheglov): remove this flag eventually.
+bool temporaryUntilPrintsRemovedEnablePrinting = true;
+
 /// Used to report an error in input.
 ///
 /// Avoid using this for reporting compile-time errors, instead use
@@ -50,7 +57,9 @@ String deprecated_printUnexpected(Uri uri, int charOffset, String message) {
     if (isVerbose) print(StackTrace.current);
     throw new deprecated_InputError(uri, charOffset, message);
   }
-  print(formattedMessage);
+  if (temporaryUntilPrintsRemovedEnablePrinting) {
+    print(formattedMessage);
+  }
   return formattedMessage;
 }