Revert "Switch FE to use the libraries.json format."

pkg/front_end/test/incremental_kernel_generator_test.dart

Index: pkg/front_end/test/incremental_kernel_generator_test.dart
diff --git a/pkg/front_end/test/incremental_kernel_generator_test.dart b/pkg/front_end/test/incremental_kernel_generator_test.dart
index c3bbeb91f4b5ef9bd6c0c8ae50cc321c2ce976aa..9195343d6e309c864bc6d5a78f016df518e07ab6 100644
--- a/pkg/front_end/test/incremental_kernel_generator_test.dart
+++ b/pkg/front_end/test/incremental_kernel_generator_test.dart
@@ -36,16 +36,18 @@ class IncrementalKernelGeneratorTest {
   /// Compute the initial [Program] for the given [entryPoint].
   Future<Program> getInitialState(Uri entryPoint,
       {bool setPackages: true}) async {
-    createSdkFiles(fileSystem);
+    Map<String, Uri> dartLibraries = createSdkFiles(fileSystem);
     // TODO(scheglov) Builder the SDK kernel and set it into the options.
 
+    // TODO(scheglov) Make `.packages` file optional.
+
     var compilerOptions = new CompilerOptions()
       ..fileSystem = fileSystem
       ..byteStore = new MemoryByteStore()
 //      ..logger = new PerformanceLog(stdout)
       ..strongMode = true
       ..chaseDependencies = true
-      ..librariesSpecificationUri = Uri.parse('file:///sdk/lib/libraries.json');
+      ..dartLibraries = dartLibraries;
 
     if (setPackages) {
       compilerOptions.packagesFileUri = Uri.parse('file:///test/.packages');