Added support for exports and re-exports.

lib/compiler/implementation/compiler.dart

Index: lib/compiler/implementation/compiler.dart
diff --git a/lib/compiler/implementation/compiler.dart b/lib/compiler/implementation/compiler.dart
index c316b5c551d46de15b61ba2de4ac126b1ea1f123..5aa454b39a26cf8c807110c9b146a4ee535428b4 100644
--- a/lib/compiler/implementation/compiler.dart
+++ b/lib/compiler/implementation/compiler.dart
@@ -383,22 +383,24 @@ class Compiler implements DiagnosticListener {
     initializeSpecialClasses();
   }
 
-  void importCoreLibrary(LibraryElement library) {
+  /**
+   * Lazily loads and returns the [LibraryElement] for the dart:core library.
+   */
+  LibraryElement importCoreLibrary(ImportExportHandler handler) {
     Uri coreUri = new Uri.fromComponents(scheme: 'dart', path: 'core');
     if (coreLibrary === null) {
-      coreLibrary = scanner.loadLibrary(coreUri, null, coreUri);
+      coreLibrary =
+          scanner.loadLibraryInternal(handler, coreUri, null, coreUri);
     }
-    scanner.importLibrary(library,
-                          coreLibrary,
-                          null,
-                          library.entryCompilationUnit);
+    return coreLibrary;
   }
 
-  void patchDartLibrary(LibraryElement library, String dartLibraryPath) {
+  void patchDartLibrary(ImportExportHandler handler,
+                        LibraryElement library, String dartLibraryPath) {
     if (library.isPatched) return;
     Uri patchUri = resolvePatchUri(dartLibraryPath);
     if (patchUri !== null) {
-      patchParser.patchLibrary(patchUri, library);
+      patchParser.patchLibrary(handler, patchUri, library);
     }
   }