Extract DiagnosticReporter implementation from Compiler.

pkg/compiler/lib/src/js_emitter/startup_emitter/model_emitter.dart

Index: pkg/compiler/lib/src/js_emitter/startup_emitter/model_emitter.dart
diff --git a/pkg/compiler/lib/src/js_emitter/startup_emitter/model_emitter.dart b/pkg/compiler/lib/src/js_emitter/startup_emitter/model_emitter.dart
index 8c9f24783129663857d57171a2125aa9e7a07ec6..ec8ac00c1c86105465ac23a8217663c3ea29bb89 100644
--- a/pkg/compiler/lib/src/js_emitter/startup_emitter/model_emitter.dart
+++ b/pkg/compiler/lib/src/js_emitter/startup_emitter/model_emitter.dart
@@ -31,6 +31,9 @@ import '../../js_backend/js_backend.dart' show
     Namer,
     ConstantEmitter;
 
+import '../../diagnostics/diagnostic_listener.dart' show
+    DiagnosticReporter;
+
 import '../../diagnostics/spannable.dart' show
     NO_LOCATION_SPANNABLE;
 
@@ -100,6 +103,8 @@ class ModelEmitter {
         constantListGenerator);
   }
 
+  DiagnosticReporter get reporter => compiler.reporter;
+
   js.Expression constantListGenerator(js.Expression array) {
     // TODO(floitsch): remove hard-coded name.
     return js.js('makeConstList(#)', [array]);
@@ -211,7 +216,7 @@ class ModelEmitter {
 
     if (backend.requiresPreamble &&
         !backend.htmlLibraryIsLoaded) {
-      compiler.reportHintMessage(
+      reporter.reportHintMessage(
           NO_LOCATION_SPANNABLE, MessageKind.PREAMBLE);
     }