Refactor handling of source map information.

pkg/compiler/lib/src/ssa/ssa.dart

Index: pkg/compiler/lib/src/ssa/ssa.dart
diff --git a/pkg/compiler/lib/src/ssa/ssa.dart b/pkg/compiler/lib/src/ssa/ssa.dart
index 2b561627b8442cb3be052587bab8a9c42e75ed7a..abc702befae152c9653dad7815f7a1e00fb6b845 100644
--- a/pkg/compiler/lib/src/ssa/ssa.dart
+++ b/pkg/compiler/lib/src/ssa/ssa.dart
@@ -18,14 +18,14 @@ import '../elements/modelx.dart'
          VariableElementX,
          ConstructorBodyElementX;
 import '../helpers/helpers.dart';
+import '../io/source_file.dart';
+import '../io/source_information.dart';
 import '../js/js.dart' as js;
 import '../js_backend/js_backend.dart';
 import '../js_emitter/js_emitter.dart' show CodeEmitterTask, NativeEmitter;
 import '../native/native.dart' as native;
 import '../scanner/scannerlib.dart'
     show PartialFunctionElement, Token, PLUS_TOKEN;
-import '../io/source_file.dart';
-import '../io/source_map_builder.dart';
 import '../tree/tree.dart' as ast;
 import '../types/types.dart';
 import '../types/constants.dart' show computeTypeMask;