Emit to StreamCodeOutput instead of CodeBuffer.

pkg/compiler/lib/src/js_backend/codegen/task.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /// Generate code using the cps-based IR pipeline.
 library code_generator_task;
 
 import 'glue.dart';
 import 'codegen.dart';
 import 'unsugar.dart';
 
 import '../js_backend.dart';
 import '../../dart2jslib.dart';
-import '../../source_file.dart';
+import '../../io/source_file.dart';
 import '../../cps_ir/cps_ir_nodes.dart' as cps;
 import '../../cps_ir/cps_ir_builder.dart';
 import '../../tree_ir/tree_ir_nodes.dart' as tree_ir;
 import '../../tree/tree.dart' as ast;
 import '../../types/types.dart' show TypeMask, UnionTypeMask, FlatTypeMask,
     ForwardingTypeMask;
 import '../../scanner/scannerlib.dart' as scanner;
 import '../../elements/elements.dart';
 import '../../closure.dart';
 import '../../js/js.dart' as js;
@@ skipping 202 matching lines @@
       endSourcePosition =
           new TokenSourceFileLocation(sourceFile, endToken, name);
     }
     return node.withPosition(sourcePosition, endSourcePosition);
   }
 
   SourceFile sourceFileOfElement(Element element) {
     return element.implementation.compilationUnit.script.file;
   }
 }