Extract DiagnosticReporter implementation from Compiler.

tests/compiler/dart2js/related_types.dart

Index: tests/compiler/dart2js/related_types.dart
diff --git a/tests/compiler/dart2js/related_types.dart b/tests/compiler/dart2js/related_types.dart
index 54d9ab873b7a2e822597648b4926892215159b76..ad52b0eea8bac7cdc036e4cdcacaa7de8b46031d 100644
--- a/tests/compiler/dart2js/related_types.dart
+++ b/tests/compiler/dart2js/related_types.dart
@@ -8,6 +8,7 @@ import 'package:compiler/src/commandline_options.dart';
 import 'package:compiler/src/compiler.dart';
 import 'package:compiler/src/core_types.dart';
 import 'package:compiler/src/dart_types.dart';
+import 'package:compiler/src/diagnostics/diagnostic_listener.dart';
 import 'package:compiler/src/diagnostics/messages.dart';
 import 'package:compiler/src/elements/elements.dart';
 import 'package:compiler/src/filenames.dart';
@@ -61,7 +62,7 @@ void checkMemberElement(Compiler compiler, MemberElement member) {
   RelatedTypesChecker relatedTypesChecker =
       new RelatedTypesChecker(compiler, resolvedAst);
   if (resolvedAst.node != null) {
-    compiler.withCurrentElement(member.implementation, () {
+    compiler.reporter.withCurrentElement(member.implementation, () {
       relatedTypesChecker.apply(resolvedAst.node);
     });
   }
@@ -79,6 +80,8 @@ class RelatedTypesChecker extends TraversalVisitor<DartType, dynamic> {
 
   CoreTypes get coreTypes => compiler.coreTypes;
 
+  DiagnosticReporter get reporter => compiler.reporter;
+
   InterfaceType get thisType => resolvedAst.element.enclosingClass.thisType;
 
   /// Returns `true` if there exists no common subtype of [left] and [right].
@@ -97,10 +100,10 @@ class RelatedTypesChecker extends TraversalVisitor<DartType, dynamic> {
   /// a hint otherwise.
   void checkRelated(Node node, DartType left, DartType right) {
     if (hasEmptyIntersection(left, right)) {
-      compiler.reportHint(compiler.createMessage(
+      reporter.reportHintMessage(
           node,
           MessageKind.NO_COMMON_SUBTYPES,
-          {'left': left, 'right': right}));
+          {'left': left, 'right': right});
     }
   }