Extract DiagnosticReporter implementation from Compiler.

pkg/compiler/lib/src/js_emitter/lazy_emitter/emitter.dart

Index: pkg/compiler/lib/src/js_emitter/lazy_emitter/emitter.dart
diff --git a/pkg/compiler/lib/src/js_emitter/lazy_emitter/emitter.dart b/pkg/compiler/lib/src/js_emitter/lazy_emitter/emitter.dart
index d68c38b6f03b49611119d95cec3501dbbfdb3465..2c2f3035430a8ca6948f90e3b48a5209daf42715 100644
--- a/pkg/compiler/lib/src/js_emitter/lazy_emitter/emitter.dart
+++ b/pkg/compiler/lib/src/js_emitter/lazy_emitter/emitter.dart
@@ -26,6 +26,9 @@ import '../js_emitter.dart' show
 import '../js_emitter.dart' as emitterTask show
     Emitter;
 
+import '../../diagnostics/diagnostic_listener.dart' show
+    DiagnosticReporter;
+
 import '../../diagnostics/spannable.dart' show
     NO_LOCATION_SPANNABLE;
 
@@ -41,6 +44,8 @@ class Emitter implements emitterTask.Emitter {
         this.namer = namer,
         _emitter = new ModelEmitter(compiler, namer, nativeEmitter);
 
+  DiagnosticReporter get reporter => _compiler.reporter;
+
   @override
   String get patchVersion => "lazy";
 
@@ -181,7 +186,7 @@ class Emitter implements emitterTask.Emitter {
         throw new UnsupportedError('createDartClosureFromNameOfStaticFunction');
 
       default:
-        _compiler.internalError(NO_LOCATION_SPANNABLE,
+        reporter.internalError(NO_LOCATION_SPANNABLE,
                                 "Unhandled Builtin: $builtin");
         return null;
     }