Create an option to disable type inference and type promotion.

pkg/front_end/lib/src/fasta/kernel/kernel_target.dart

 // Copyright (c) 2016, 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.
 
 library fasta.kernel_target;
 
 import 'dart:async' show Future;
 
 import 'dart:io' show File;
 
@@ skipping 83 matching lines @@
 
   Program program;
 
   final List<String> errors = <String>[];
 
   final TypeBuilder dynamicType =
       new KernelNamedTypeBuilder("dynamic", null, -1, null);
 
   bool get strongMode => backendTarget.strongMode;
 
+  bool get disableTypeInference => backendTarget.disableTypeInference;
+
   KernelTarget(
       this.fileSystem, DillTarget dillTarget, TranslateUri uriTranslator,
       [Map<String, Source> uriToSource])
       : dillTarget = dillTarget,
         uriToSource = uriToSource ?? CompilerContext.current.uriToSource,
         super(dillTarget.ticker, uriTranslator, dillTarget.backendTarget) {
     resetCrashReporting();
     loader = createLoader();
   }
 
@@ skipping 612 matching lines @@
   }
   for (Constructor constructor in superclass.constructors) {
     if (constructor.name.name.isEmpty) {
       return constructor.function.requiredParameterCount == 0
           ? constructor
           : null;
     }
   }
   return null;
 }