Create and test source mapping for invocations.

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

Index: pkg/compiler/lib/src/js_backend/js_backend.dart
diff --git a/pkg/compiler/lib/src/js_backend/js_backend.dart b/pkg/compiler/lib/src/js_backend/js_backend.dart
index d44688ab3d667401c5c540cc59623c582114b913..0d780cb1ebaf6edc8b20761d720d0a51a6f5db3b 100644
--- a/pkg/compiler/lib/src/js_backend/js_backend.dart
+++ b/pkg/compiler/lib/src/js_backend/js_backend.dart
@@ -21,9 +21,17 @@ import '../dart2jslib.dart';
 import '../dart_types.dart';
 import '../elements/elements.dart';
 import '../io/code_output.dart';
-import '../io/source_information.dart' show SourceInformationFactory;
+import '../io/source_information.dart' show
+    SourceInformationStrategy,
+    useNewSourceInfo;
+import '../io/position_information.dart' show
+    PositionSourceInformationStrategy;
+import '../io/start_end_information.dart' show
+    StartEndSourceInformationStrategy;
 import '../js/js.dart' as jsAst;
 import '../js/js.dart' show js;
+import '../js/js_source_mapping.dart' show
+    JavaScriptSourceInformationStrategy;
 import '../js_emitter/js_emitter.dart'
     show Emitter,
          CodeEmitterTask,