Deprecate all diagnostics methods that use strings.

pkg/front_end/lib/kernel_generator.dart

Index: pkg/front_end/lib/kernel_generator.dart
diff --git a/pkg/front_end/lib/kernel_generator.dart b/pkg/front_end/lib/kernel_generator.dart
index e0ba4c782e326b5dcb2b06f745b1e2e2acdbd823..6c8bc216a46b3f0e6c1bb8906fcff66ee4a0e147 100644
--- a/pkg/front_end/lib/kernel_generator.dart
+++ b/pkg/front_end/lib/kernel_generator.dart
@@ -10,7 +10,7 @@ import 'dart:async' show Future;
 import 'dart:async';
 import 'package:front_end/src/base/processed_options.dart';
 import 'src/fasta/dill/dill_target.dart' show DillTarget;
-import 'src/fasta/errors.dart' show InputError;
+import 'src/fasta/deprecated_problems.dart' show deprecated_InputError;
 import 'src/fasta/kernel/kernel_target.dart' show KernelTarget;
 import 'package:kernel/kernel.dart' show Program;
 import 'package:kernel/target/targets.dart' show TargetFlags;
@@ -83,8 +83,8 @@ Future<Program> kernelForProgram(Uri source, CompilerOptions options) async {
       // sources for the sdk, only external references.
     }
     return program;
-  } on InputError catch (e) {
-    options.onError(new SimpleError(e.format()));
+  } on deprecated_InputError catch (e) {
+    options.onError(new SimpleError(e.deprecated_format()));
     return null;
   }
 }
@@ -179,8 +179,8 @@ Future<Program> kernelForBuildUnit(
     }
 
     return program;
-  } on InputError catch (e) {
-    options.onError(new SimpleError(e.format()));
+  } on deprecated_InputError catch (e) {
+    options.onError(new SimpleError(e.deprecated_format()));
     return null;
   }
 }