Move dart2jslib parts into separate libraries.

pkg/compiler/lib/src/mirrors_used.dart

Index: pkg/compiler/lib/src/mirrors_used.dart
diff --git a/pkg/compiler/lib/src/mirrors_used.dart b/pkg/compiler/lib/src/mirrors_used.dart
index ec535c77e53bd9885155c0105f3c8e82d4741fd7..48f3325efbb41b12402bc5c742b73a03d1191760 100644
--- a/pkg/compiler/lib/src/mirrors_used.dart
+++ b/pkg/compiler/lib/src/mirrors_used.dart
@@ -13,19 +13,14 @@ import 'constants/values.dart' show
     ListConstantValue,
     StringConstantValue,
     TypeConstantValue;
-
 import 'dart_types.dart' show
     DartType,
     InterfaceType,
     TypeKind;
-
 import 'dart2jslib.dart' show
     Compiler,
     CompilerTask,
-    MessageKind,
-    TreeElements,
     invariant;
-
 import 'elements/elements.dart' show
     ClassElement,
     Element,
@@ -33,14 +28,16 @@ import 'elements/elements.dart' show
     MetadataAnnotation,
     ScopeContainerElement,
     VariableElement;
-
+import 'messages.dart' show
+    MessageKind;
+import 'resolution/resolution.dart' show
+    TreeElements;
 import 'tree/tree.dart' show
     Import,
     LibraryTag,
     NamedArgument,
     NewExpression,
     Node;
-
 import 'util/util.dart' show
     Link,
     Spannable;