Deprecate all diagnostics methods that use strings.

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

Index: pkg/front_end/lib/src/fasta/compile_platform.dart
diff --git a/pkg/front_end/lib/src/fasta/compile_platform.dart b/pkg/front_end/lib/src/fasta/compile_platform.dart
index 750d2da3d417c46e5905232aa58d87430669fd4f..72060b41fff591ee4ddcbc9bdaf941e711d91d9e 100644
--- a/pkg/front_end/lib/src/fasta/compile_platform.dart
+++ b/pkg/front_end/lib/src/fasta/compile_platform.dart
@@ -14,7 +14,7 @@ import 'compiler_context.dart' show CompilerContext;
 
 import 'dill/dill_target.dart' show DillTarget;
 
-import 'errors.dart' show InputError;
+import 'deprecated_problems.dart' show deprecated_InputError;
 
 import 'kernel/kernel_target.dart' show KernelTarget;
 
@@ -33,9 +33,9 @@ Future mainEntryPoint(List<String> arguments) async {
     }
     try {
       await compilePlatform(arguments);
-    } on InputError catch (e) {
+    } on deprecated_InputError catch (e) {
       exitCode = 1;
-      print(e.format());
+      print(e.deprecated_format());
       return null;
     }
   }