Add optional message to assert in Dart2js.

pkg/compiler/lib/src/common/codegen.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.
 
 library dart2js.common.codegen;
 
 import '../compiler.dart' show
     Compiler;
 import '../constants/values.dart' show
     ConstantValue;
@@ skipping 38 matching lines @@
 
   Element get currentElement => treeElements.analyzedElement;
 
   // TODO(johnniwinther): Remove this getter when [Registry] creates a
   // dependency node.
   Setlet<Element> get otherDependencies => treeElements.otherDependencies;
 
   CodegenEnqueuer get world => compiler.enqueuer.codegen;
   JavaScriptBackend get backend => compiler.backend;
 
+  void registerAssert() {
+    registerStaticInvocation(backend.assertConditionHelperMethod);
+    registerStaticInvocation(backend.assertThrowMethod);
+  }
+
   void registerDependency(Element element) {
     treeElements.registerDependency(element);
   }
 
   void registerInlining(Element inlinedElement, Element context) {
     if (compiler.dumpInfo) {
       compiler.dumpInfoTask.registerInlined(inlinedElement, context);
     }
   }
 
@@ skipping 128 matching lines @@
 
   TreeElements get resolutionTree => element.resolvedAst.elements;
 
   WorldImpact run(Compiler compiler, CodegenEnqueuer world) {
     if (world.isProcessed(element)) return const WorldImpact();
 
     registry = new CodegenRegistry(compiler, resolutionTree);
     return compiler.codegen(this, world);
   }
 }