Use FileSystem to read files in SourceLoader and TranslateUri.

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 4673227363e454df733e9aea679a6ea286da16ff..c421a7ca7886f352bd5d296ff0aac2c7e531db0d 100644
--- a/pkg/front_end/test/fasta/testing/suite.dart
+++ b/pkg/front_end/test/fasta/testing/suite.dart
@@ -10,6 +10,7 @@ import 'dart:io' show File;
 
 import 'dart:convert' show JSON;
 
+import 'package:front_end/physical_file_system.dart';
 import 'package:front_end/src/fasta/testing/validating_instrumentation.dart'
     show ValidatingInstrumentation;
 
@@ -118,7 +119,8 @@ class FastaContext extends ChainContext {
     Uri sdk = await computePatchedSdk();
     Uri vm = computeDartVm(sdk);
     Uri packages = Uri.base.resolve(".packages");
-    TranslateUri uriTranslator = await TranslateUri.parse(packages);
+    TranslateUri uriTranslator =
+        await TranslateUri.parse(PhysicalFileSystem.instance, packages);
     bool strongMode = environment.containsKey(STRONG_MODE);
     bool updateExpectations = environment["updateExpectations"] == "true";
     String astKindString = environment[AST_KIND_INDEX];
@@ -180,7 +182,8 @@ class Outline extends Step<TestDescription, Program, FastaContext> {
       ..setProgram(platform);
     KernelTarget sourceTarget = astKind == AstKind.Analyzer
         ? new AnalyzerTarget(dillTarget, context.uriTranslator, strongMode)
-        : new KernelTarget(dillTarget, context.uriTranslator, strongMode);
+        : new KernelTarget(PhysicalFileSystem.instance, dillTarget,
+            context.uriTranslator, strongMode);
 
     Program p;
     try {