Let the dart2dart compiler stop in case of failure.

pkg/compiler/lib/src/js_backend/backend.dart

 // Copyright (c) 2012, 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.
 
 part of js_backend;
 
 const VERBOSE_OPTIMIZER_HINTS = false;
 
 const bool USE_CPS_IR = const bool.fromEnvironment("USE_CPS_IR");
 
@@ skipping 423 matching lines @@
   /// Resolution and codegen support for generating table of interceptors and
   /// constructors for custom elements.
   CustomElementsAnalysis customElementsAnalysis;
 
   JavaScriptConstantTask constantCompilerTask;
 
   JavaScriptResolutionCallbacks resolutionCallbacks;
 
   PatchResolverTask patchResolverTask;
 
+  bool get canHandleCompilationFailed => true;
+
   JavaScriptBackend(Compiler compiler, bool generateSourceMap)
       : namer = determineNamer(compiler),
         oneShotInterceptors = new Map<String, Selector>(),
         interceptedElements = new Map<String, Set<Element>>(),
         rti = new RuntimeTypes(compiler),
         specializedGetInterceptors = new Map<String, Set<ClassElement>>(),
         super(compiler) {
     emitter = new CodeEmitterTask(compiler, namer, generateSourceMap);
     typeVariableHandler = new TypeVariableHandler(this);
     customElementsAnalysis = new CustomElementsAnalysis(this);
@@ skipping 2071 matching lines @@
   }
 }
 
 /// Records that [constant] is used by the element behind [registry].
 class Dependency {
   final ConstantValue constant;
   final Element annotatedElement;
 
   const Dependency(this.constant, this.annotatedElement);
 }