Add optional message to assert in Dart2js.

pkg/compiler/lib/src/resolution/registry.dart

Index: pkg/compiler/lib/src/resolution/registry.dart
diff --git a/pkg/compiler/lib/src/resolution/registry.dart b/pkg/compiler/lib/src/resolution/registry.dart
index 552914c572a93df97820ff63795ee7ed86f8e5a9..d60792d9b59ce8e5f60890ca2ef911dc8fce545b 100644
--- a/pkg/compiler/lib/src/resolution/registry.dart
+++ b/pkg/compiler/lib/src/resolution/registry.dart
@@ -56,6 +56,11 @@ class EagerRegistry implements Registry {
   Iterable<Element> get otherDependencies => mapping.otherDependencies;
 
   @override
+  void registerAssert() {
+    // TODO(johnniwinther): Do something here?
+  }
+
+  @override
   void registerDependency(Element element) {
     mapping.registerDependency(element);
   }
@@ -580,13 +585,8 @@ class ResolutionRegistry implements Registry {
     world.registerInstantiatedType(type, this);
   }
 
-  void registerAssert(Send node) {
-    mapping.setAssert(node);
-    backend.resolutionCallbacks.onAssert(node, this);
-  }
-
-  bool isAssert(Send node) {
-    return mapping.isAssert(node);
+  void registerAssert() {
+    backend.resolutionCallbacks.onAssert(this);
   }
 
   void registerSendStructure(Send node, SendStructure sendStructure) {