Move Compiler.libraries to LibraryLoader.

tests/compiler/dart2js/deferred_follow_implicit_super_regression_test.dart

 // Copyright (c) 2014, 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.
 
 import 'package:expect/expect.dart';
 import "package:async_helper/async_helper.dart";
 import 'memory_source_file_helper.dart';
 import "memory_compiler.dart";
 import "dart:async";
 
 import 'package:compiler/implementation/dart2jslib.dart'
        as dart2js;
 
 runTest(String mainScript, test) {
   Compiler compiler = compilerFor(MEMORY_SOURCE_FILES,
       outputProvider: new OutputCollector());
   asyncTest(() => compiler.run(Uri.parse(mainScript))
       .then((_) => test(compiler)));
 }
 
 void main() {
   runTest('memory:main.dart', (compiler) {
+    lookupLibrary(name) {
+      return compiler.libraryLoader.lookupLibrary(Uri.parse(name));
+    }
+
     var main = compiler.mainApp.find(dart2js.Compiler.MAIN);
     Expect.isNotNull(main, "Could not find 'main'");
     compiler.deferredLoadTask.onResolutionComplete(main);
 
     var outputUnitForElement = compiler.deferredLoadTask.outputUnitForElement;
 
-    var lib = compiler.libraries["memory:lib.dart"];
+    var lib = lookupLibrary("memory:lib.dart");
     var a = lib.find("a");
     var b = lib.find("b");
     var c = lib.find("c");
     var d = lib.find("d");
     Expect.equals(outputUnitForElement(a), outputUnitForElement(b));
     Expect.equals(outputUnitForElement(a), outputUnitForElement(c));
     Expect.equals(outputUnitForElement(a), outputUnitForElement(d));
   });
 }
 
@@ skipping 67 matching lines @@
 class D2 {
   D2(x) {
     d();
   }
 }
 
 // Implicit redirecting "super" call with a parameter via mixin.
 class D3 = D2 with D1;
 """,
 };