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 f0e83debdde8babd1ab14f41d9ca46024330138b..5a78aebb613656459a9e50e4d5a1b8e179d72647 100644
--- a/lib/compiler/implementation/compiler.dart
+++ b/lib/compiler/implementation/compiler.dart
@@ -162,6 +162,7 @@ abstract class Compiler implements DiagnosticListener {
   DietParserTask dietParser;
   ParserTask parser;
   PatchParserTask patchParser;
+  LibraryLoader libraryLoader;
   TreeValidatorTask validator;
   ResolverTask resolver;
   closureMapping.ClosureTask closureToClassMapper;
@@ -207,6 +208,7 @@ abstract class Compiler implements DiagnosticListener {
     dietParser = new DietParserTask(this);
     parser = new ParserTask(this);
     patchParser = new PatchParserTask(this);
+    libraryLoader = new LibraryLoaderTask(this);
     validator = new TreeValidatorTask(this);
     resolver = new ResolverTask(this);
     closureToClassMapper = new closureMapping.ClosureTask(this);
@@ -394,31 +396,12 @@ abstract class Compiler implements DiagnosticListener {
 
   void loadCoreImplLibrary() {
     Uri coreImplUri = new Uri.fromComponents(scheme: 'dart', path: 'coreimpl');
-    coreImplLibrary = scanner.loadLibrary(coreImplUri, null, coreImplUri);
+    coreImplLibrary = libraryLoader.loadLibrary(coreImplUri, null, coreImplUri);
   }
 
   void importHelperLibrary(LibraryElement library) {
     if (jsHelperLibrary !== null) {
-      scanner.importLibrary(library, jsHelperLibrary, null);
-    }
-  }
-
-  void importCoreLibrary(LibraryElement library) {
-    if (coreLibrary === null) {
-      Uri coreUri = new Uri.fromComponents(scheme: 'dart', path: 'core');
-      coreLibrary = scanner.loadLibrary(coreUri, null, coreUri);
-    }
-    scanner.importLibrary(library,
-                          coreLibrary,
-                          null,
-                          library.entryCompilationUnit);
-  }
-
-  void patchDartLibrary(LibraryElement library, String dartLibraryPath) {
-    if (library.isPatched) return;
-    Uri patchUri = resolvePatchUri(dartLibraryPath);
-    if (patchUri !== null) {
-      patchParser.patchLibrary(patchUri, library);
+      libraryLoader.importLibrary(this, library, jsHelperLibrary, null);
     }
   }
 
@@ -465,7 +448,7 @@ abstract class Compiler implements DiagnosticListener {
   void runCompiler(Uri uri) {
     log('compiling $uri ($BUILD_ID)');
     scanBuiltinLibraries();
-    mainApp = scanner.loadLibrary(uri, null, uri);
+    mainApp = libraryLoader.loadLibrary(uri, null, uri);
     libraries.forEach((_, library) {
       maybeEnableJSHelper(library);
     });
@@ -861,5 +844,8 @@ bool invariant(Spannable spannable, var condition, {String message: null}) {
   if (condition is Function){
     condition = condition();
   }
+  if (!condition && message != null) {
+    print('assertion failed: $message');
+  }
   return spannable != null && condition;
 }