Report messages instead of just printing.

pkg/front_end/lib/src/kernel_generator_impl.dart

 // Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /// Defines the front-end API for converting source code to Dart Kernel objects.
 library front_end.kernel_generator_impl;
 
 import 'dart:async' show Future;
 import 'dart:async';
 
@@ skipping 129 matching lines @@
             dillTarget.loader.libraries.map((lib) => lib.importUri).toSet();
         trimProgram(program, (uri) => !excluded.contains(uri));
       }
       if (options.debugDump) {
         printProgramText(program, libraryFilter: kernelTarget.isSourceLibrary);
       }
       options.ticker.logMs("Generated program");
     }
 
     if (kernelTarget.errors.isNotEmpty) {
-      kernelTarget.errors.forEach(options.deprecated_reportError);
+      // TODO(ahe): The errors have already been reported via CompilerContext.
+      kernelTarget.errors.forEach(options.reportMessage);
       return null;
     }
 
     return new CompilerResult(
         summary: summary,
         program: program,
         deps: kernelTarget.loader.getDependencies());
   } on deprecated_InputError catch (e) {
-    options.deprecated_reportError(e.deprecated_format());
+    options.reportMessage(deprecated_InputError.toMessage(e));
     return null;
   } catch (e, t) {
     return reportCrash(e, t);
   }
 }
 
 /// Result object of [generateKernel].
 class CompilerResult {
   /// The generated summary bytes, if it was requested.
   final List<int> summary;
 
   /// The generated program, if it was requested.
   final Program program;
 
   /// Dependencies traversed by the compiler. Used only for generating
   /// dependency .GN files in the dart-sdk build system.
   /// Note this might be removed when we switch to compute depencencies without
   /// using the compiler itself.
   final List<Uri> deps;
 
   CompilerResult({this.summary, this.program, this.deps});
 }