Revert r22847: some dart2dart tests fail.

tests/compiler/dart2js/mock_compiler.dart

Index: tests/compiler/dart2js/mock_compiler.dart
===================================================================
--- tests/compiler/dart2js/mock_compiler.dart	(revision 22847)
+++ tests/compiler/dart2js/mock_compiler.dart	(working copy)
@@ -172,7 +172,6 @@
   class _WorkerBase {}''';
 
 class MockCompiler extends Compiler {
-  api.DiagnosticHandler diagnosticHandler;
   List<WarningMessage> warnings;
   List<WarningMessage> errors;
   final Map<String, SourceFile> sourceFiles;
@@ -256,8 +255,6 @@
   void reportWarning(Node node, var message) {
     if (message is! Message) message = message.message;
     warnings.add(new WarningMessage(node, message));
-    reportDiagnostic(spanFromNode(node),
-        'Warning: $message', api.Diagnostic.WARNING);
   }
 
   void reportError(Node node, var message) {
@@ -267,8 +264,6 @@
     }
     if (message is! Message) message = message.message;
     errors.add(new WarningMessage(node, message));
-    reportDiagnostic(spanFromNode(node),
-        'Error: $message', api.Diagnostic.ERROR);
   }
 
   void reportMessage(SourceSpan span, var message, api.Diagnostic kind) {
@@ -278,17 +273,10 @@
     } else {
       warnings.add(diagnostic);
     }
-    reportDiagnostic(span, "$message", kind);
   }
 
-  void reportDiagnostic(SourceSpan span, String message, api.Diagnostic kind) {
-    if (diagnosticHandler != null) {
-      if (span != null) {
-        diagnosticHandler(span.uri, span.begin, span.end, message, kind);
-      } else {
-        diagnosticHandler(null, null, null, message, kind);
-      }
-    }
+  void reportDiagnostic(SourceSpan span, String message, var kind) {
+    print(message);
   }
 
   bool get compilationFailed => !errors.isEmpty;
@@ -330,7 +318,7 @@
 
   parseScript(String text, [LibraryElement library]) {
     if (library == null) library = mainApp;
-    parseUnit(text, this, library, registerSource);
+    parseUnit(text, this, library);
   }
 
   void scanBuiltinLibraries() {