Move dart2jslib parts into separate libraries.

pkg/compiler/lib/src/elements/elements.dart

Index: pkg/compiler/lib/src/elements/elements.dart
diff --git a/pkg/compiler/lib/src/elements/elements.dart b/pkg/compiler/lib/src/elements/elements.dart
index f55e198ed979ce0042002dec781ab7df7e338e6c..79229a90ee55abfb45917da170ac6c754a4ad1c9 100644
--- a/pkg/compiler/lib/src/elements/elements.dart
+++ b/pkg/compiler/lib/src/elements/elements.dart
@@ -6,33 +6,23 @@ library elements;
 
 import '../constants/constructors.dart';
 import '../constants/expressions.dart';
-import '../tree/tree.dart';
-import '../util/util.dart';
-import '../resolution/resolution.dart';
-
-import '../dart2jslib.dart' show InterfaceType,
-                                 DartType,
-                                 TypeVariableType,
-                                 TypedefType,
-                                 DualKind,
-                                 MessageKind,
-                                 DiagnosticListener,
-                                 Script,
-                                 FunctionType,
-                                 Selector,
-                                 SourceSpan,
-                                 Constant,
-                                 Compiler,
-                                 Backend,
-                                 isPrivateName;
-
 import '../dart_types.dart';
-
-import '../scanner/scannerlib.dart' show Token,
-                                         isUserDefinableOperator,
-                                         isMinusOperator;
-
+import '../dart2jslib.dart' show
+    Backend,
+    Compiler,
+    isPrivateName,
+    SourceSpan;
+import '../diagnostic_listener.dart';
+import '../messages.dart' show MessageKind;
+import '../resolution/resolution.dart';
 import '../ordered_typeset.dart' show OrderedTypeSet;
+import '../scanner/scannerlib.dart' show
+    Token,
+    isUserDefinableOperator,
+    isMinusOperator;
+import '../script.dart';
+import '../tree/tree.dart';
+import '../util/util.dart';
 
 import 'visitor.dart' show ElementVisitor;