Add ImportElement and ExportElement

pkg/compiler/lib/src/dump_info.dart

Index: pkg/compiler/lib/src/dump_info.dart
diff --git a/pkg/compiler/lib/src/dump_info.dart b/pkg/compiler/lib/src/dump_info.dart
index 4ba2073fe031dd097bc327f5e4533420d2be67cc..adf558da45719ba509e00fe55f70c68a9210b56f 100644
--- a/pkg/compiler/lib/src/dump_info.dart
+++ b/pkg/compiler/lib/src/dump_info.dart
@@ -82,8 +82,7 @@ class ElementInfoCollector extends BaseElementVisitor<Info, dynamic> {
   }
 
   LibraryInfo visitLibraryElement(LibraryElement element, _) {
-    String libname = element.getLibraryName();
-    libname = libname == "" ? "<unnamed>" : libname;
+    String libname = element.hasLibraryName ? element.libraryName : "<unnamed>";
     int size = compiler.dumpInfoTask.sizeOf(element);
     LibraryInfo info =
       new LibraryInfo(libname, element.canonicalUri, null, size);