Add ImportElement and ExportElement

pkg/compiler/lib/src/ssa/builder.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of ssa;
 
 class SsaFunctionCompiler implements FunctionCompiler {
   final SsaCodeGeneratorTask generator;
   final SsaBuilderTask builder;
   final SsaOptimizerTask optimizer;
@@ skipping 3322 matching lines @@
   }
 
   /// Inserts a call to checkDeferredIsLoaded for [prefixElement].
   /// If [prefixElement] is [null] ndo nothing.
   void generateIsDeferredLoadedCheckIfNeeded(PrefixElement prefixElement,
                                              ast.Node location) {
     if (prefixElement == null) return;
     String loadId =
         compiler.deferredLoadTask.getImportDeferName(location, prefixElement);
     HInstruction loadIdConstant = addConstantString(loadId);
-    String uri = prefixElement.deferredImport.uri.dartString.slowToString();
+    String uri = prefixElement.deferredImport.uri.toString();
     HInstruction uriConstant = addConstantString(uri);
     Element helper = backend.getCheckDeferredIsLoaded();
     pushInvokeStatic(location, helper, [loadIdConstant, uriConstant]);
     pop();
   }
 
   /// Inserts a call to checkDeferredIsLoaded if the send has a prefix that
   /// resolves to a deferred library.
   void generateIsDeferredLoadedCheckOfSend(ast.Send node) {
     generateIsDeferredLoadedCheckIfNeeded(
@@ skipping 5585 matching lines @@
     if (unaliased is TypedefType) throw 'unable to unalias $type';
     unaliased.accept(this, builder);
   }
 
   void visitDynamicType(DynamicType type, SsaBuilder builder) {
     JavaScriptBackend backend = builder.compiler.backend;
     ClassElement cls = backend.findHelper('DynamicRuntimeType');
     builder.push(new HDynamicType(type, new TypeMask.exact(cls, classWorld)));
   }
 }