Create Namer and Emitter on codegen start.

pkg/compiler/lib/src/js_emitter/full_emitter/interceptor_emitter.dart

Index: pkg/compiler/lib/src/js_emitter/full_emitter/interceptor_emitter.dart
diff --git a/pkg/compiler/lib/src/js_emitter/full_emitter/interceptor_emitter.dart b/pkg/compiler/lib/src/js_emitter/full_emitter/interceptor_emitter.dart
index 0da9ca3a5826dcccb33eb67adf72c6acc58e4fe9..1c90f923ed599f876fe14a92c097362d7dafba3e 100644
--- a/pkg/compiler/lib/src/js_emitter/full_emitter/interceptor_emitter.dart
+++ b/pkg/compiler/lib/src/js_emitter/full_emitter/interceptor_emitter.dart
@@ -5,8 +5,11 @@
 part of dart2js.js_emitter.full_emitter;
 
 class InterceptorEmitter extends CodeEmitterHelper {
+  final ClosedWorld closedWorld;
   final Set<jsAst.Name> interceptorInvocationNames = new Set<jsAst.Name>();
 
+  InterceptorEmitter(this.closedWorld);
+
   void recordMangledNameOfMemberMethod(
       FunctionElement member, jsAst.Name name) {
     if (backend.isInterceptedMethod(member)) {
@@ -17,7 +20,7 @@ class InterceptorEmitter extends CodeEmitterHelper {
   jsAst.Expression buildGetInterceptorMethod(
       jsAst.Name key, Set<ClassElement> classes) {
     InterceptorStubGenerator stubGenerator =
-        new InterceptorStubGenerator(compiler, namer, backend);
+        new InterceptorStubGenerator(compiler, namer, backend, closedWorld);
     jsAst.Expression function =
         stubGenerator.generateGetInterceptorMethod(classes);
 
@@ -53,7 +56,7 @@ class InterceptorEmitter extends CodeEmitterHelper {
       ..sort();
 
     InterceptorStubGenerator stubGenerator =
-        new InterceptorStubGenerator(compiler, namer, backend);
+        new InterceptorStubGenerator(compiler, namer, backend, closedWorld);
     String globalObject =
         namer.globalObjectFor(backend.helpers.interceptorsLibrary);
     for (jsAst.Name name in names) {