Extract DiagnosticReporter implementation from Compiler.

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

Index: pkg/compiler/lib/src/js_emitter/full_emitter/class_emitter.dart
diff --git a/pkg/compiler/lib/src/js_emitter/full_emitter/class_emitter.dart b/pkg/compiler/lib/src/js_emitter/full_emitter/class_emitter.dart
index c5723ae8d5095b323a8a2dc194add7026d88e52e..5a84ef2252aa13ae986dc5f381bd95ffd039f2de 100644
--- a/pkg/compiler/lib/src/js_emitter/full_emitter/class_emitter.dart
+++ b/pkg/compiler/lib/src/js_emitter/full_emitter/class_emitter.dart
@@ -156,7 +156,7 @@ class ClassEmitter extends CodeEmitterHelper {
 
           int code = field.getterFlags + (field.setterFlags << 2);
           if (code == 0) {
-            compiler.internalError(fieldElement,
+            reporter.internalError(fieldElement,
                 'Field code is 0 ($fieldElement).');
           }
           fieldNameParts.add(
@@ -212,7 +212,7 @@ class ClassEmitter extends CodeEmitterHelper {
 
     for (Field field in cls.fields) {
       Element member = field.element;
-      compiler.withCurrentElement(member, () {
+      reporter.withCurrentElement(member, () {
         if (field.needsGetter) {
           emitGetterForCSP(member, field.name, field.accessorName, builder);
         }