Generate outline without transformations in patched_sdk, use it for unit tests

pkg/front_end/test/fasta/testing/suite.dart

Index: pkg/front_end/test/fasta/testing/suite.dart
diff --git a/pkg/front_end/test/fasta/testing/suite.dart b/pkg/front_end/test/fasta/testing/suite.dart
index f08f6cded4ebb3aca14f163ddcfd4558a486eded..e4e320c090e41e215e8d742570fe54e24802dc3f 100644
--- a/pkg/front_end/test/fasta/testing/suite.dart
+++ b/pkg/front_end/test/fasta/testing/suite.dart
@@ -82,11 +82,14 @@ class FastaContext extends ChainContext {
   final TranslateUri uriTranslator;
   final List<Step> steps;
   final Uri vm;
+  Uri sdk;
+  Uri platformUri;
+  Uri outlineUri;
 
   final ExpectationSet expectationSet =
       new ExpectationSet.fromJsonList(JSON.decode(EXPECTATIONS));
 
-  Future<Program> platform;
+  Future<Program> outline;
 
   FastaContext(
       this.vm,
@@ -114,10 +117,18 @@ class FastaContext extends ChainContext {
     }
   }
 
-  Future<Program> loadPlatform() {
-    return platform ??= new Future<Program>(() async {
-      Uri sdk = await computePatchedSdk();
-      return loadProgramFromBinary(sdk.resolve('platform.dill').toFilePath());
+  Future ensurePlatformUris() async {
+    if (sdk == null) {
+      sdk = await computePatchedSdk();
+      platformUri = sdk.resolve('platform.dill');
+      outlineUri = sdk.resolve('outline.dill');
+    }
+  }
+
+  Future<Program> loadPlatformOutline() {
+    return outline ??= new Future<Program>(() async {
+      await ensurePlatformUris();
+      return loadProgramFromBinary(outlineUri.toFilePath());
     });
   }
 
@@ -160,8 +171,10 @@ class Run extends Step<Uri, int, FastaContext> {
     File generated = new File.fromUri(uri);
     StdioProcess process;
     try {
-      process = await StdioProcess
-          .run(context.vm.toFilePath(), [generated.path, "Hello, World!"]);
+      await context.ensurePlatformUris();

[ahe, 2017/05/31 14:04:40]

You can't do this here because this step is "async".

[Siggi Cherem (dart-lang), 2017/05/31 15:44:04]

Should this just assert that context.patformUri is not null? (I mean, in
practice this step is done after other steps that do ensure that the platforms
uris are there. So asserting this would be a way to ensure that you put the Run
step after some Setup step.) If not, what's the appropriate way to handle this?

[ahe, 2017/05/31 16:40:18]

I wasn't able to provide you a general solution for this earlier, but now it's
obvious to me :-)

Simply add another step.

But in this particular case, an assertion should be enough.

+      var platformDill = context.platformUri.toFilePath();
+      var args = ['--platform=$platformDill', generated.path, "Hello, World!"];
+      process = await StdioProcess.run(context.vm.toFilePath(), args);
       print(process.output);
     } finally {
       generated.parent.delete(recursive: true);
@@ -190,10 +203,10 @@ class Outline extends Step<TestDescription, Program, FastaContext> {
 
   Future<Result<Program>> run(
       TestDescription description, FastaContext context) async {
-    Program platform = await context.loadPlatform();
+    Program platformOutline = await context.loadPlatformOutline();
     Ticker ticker = new Ticker();
     DillTarget dillTarget = new DillTarget(ticker, context.uriTranslator);
-    dillTarget.loader.appendLibraries(platform);
+    dillTarget.loader.appendLibraries(platformOutline);
     KernelTarget sourceTarget = astKind == AstKind.Analyzer
         ? new AnalyzerTarget(dillTarget, context.uriTranslator, strongMode)
         : new KernelTarget(PhysicalFileSystem.instance, dillTarget,