Create LibraryElement with SDK context for SDK sources.

pkg/analyzer/test/src/task/dart_test.dart

Index: pkg/analyzer/test/src/task/dart_test.dart
diff --git a/pkg/analyzer/test/src/task/dart_test.dart b/pkg/analyzer/test/src/task/dart_test.dart
index 2a9fca8309b6a3ba13300eb33bfca39d6518b2f5..9ebd8b9947864a074a7a26847b5429e189f51e1f 100644
--- a/pkg/analyzer/test/src/task/dart_test.dart
+++ b/pkg/analyzer/test/src/task/dart_test.dart
@@ -12,6 +12,7 @@ import 'package:analyzer/src/generated/engine.dart'
     show AnalysisOptionsImpl, CacheState;
 import 'package:analyzer/src/generated/error.dart';
 import 'package:analyzer/src/generated/resolver.dart';
+import 'package:analyzer/src/generated/sdk.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/task/dart.dart';
 import 'package:analyzer/task/dart.dart';
@@ -399,6 +400,22 @@ library libB;
     }
   }
 
+  test_perform_dartCoreContext() {
+    List<Source> sources = newSources({'/libA.dart': ''});
+    Source source = sources[0];
+    // perform task
+    _computeResult(source, LIBRARY_ELEMENT2);
+    expect(task, new isInstanceOf<BuildDirectiveElementsTask>());
+    // prepare outputs
+    LibraryElement libraryElement = outputs[LIBRARY_ELEMENT2];
+    // verify that dart:core has SDK context
+    {
+      LibraryElement coreLibrary = libraryElement.importedLibraries[0];
+      DartSdk dartSdk = context.sourceFactory.dartSdk;
+      expect(coreLibrary.context, same(dartSdk.context));
+    }
+  }
+
   test_perform_error_exportOfNonLibrary() {
     List<Source> sources = newSources({
       '/libA.dart': '''