Change dart2js.dart to use compiler_new.dart

pkg/compiler/lib/src/source_file_provider.dart

Index: pkg/compiler/lib/src/source_file_provider.dart
diff --git a/pkg/compiler/lib/src/source_file_provider.dart b/pkg/compiler/lib/src/source_file_provider.dart
index da154195c312ebffb08e74dcb87089b446ac043d..7fae6f2dc29c03f43885d2376d5138f70271e4ed 100644
--- a/pkg/compiler/lib/src/source_file_provider.dart
+++ b/pkg/compiler/lib/src/source_file_provider.dart
@@ -238,7 +238,7 @@ class FormattingDiagnosticHandler implements CompilerDiagnostics {
 
 typedef void MessageCallback(String message);
 
-class RandomAccessFileOutputProvider {
+class RandomAccessFileOutputProvider implements CompilerOutput {
   final Uri out;
   final Uri sourceMapOut;
   final MessageCallback onInfo;
@@ -262,6 +262,10 @@ class RandomAccessFileOutputProvider {
   }
 
   EventSink<String> call(String name, String extension) {
+    return createEventSink(name, extension);
+  }
+  
+  EventSink<String> createEventSink(String name, String extension) {
     Uri uri;
     bool isPrimaryOutput = false;
     // TODO (johnniwinther, sigurdm): Make a better interface for