Start preparing tests to accept binary compiler input.

pkg/compiler/lib/src/source_file_provider.dart

 // Copyright (c) 2013, 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.
 
 library source_file_provider;
 
 import 'dart:async';
-import 'dart:convert';
 import 'dart:io';
 import 'dart:math' as math;
 import 'dart:typed_data';
 
 import '../compiler.dart' as api show Diagnostic;
 import '../compiler_new.dart' as api;
 import '../compiler_new.dart';
 import 'colors.dart' as colors;
 import 'dart2js.dart' show AbortLeg;
 import 'filenames.dart';
 import 'io/source_file.dart';
 import 'util/uri_extras.dart';
 
 abstract class SourceFileProvider implements CompilerInput {
   bool isWindows = (Platform.operatingSystem == 'windows');
   Uri cwd = currentDirectory;
   Map<Uri, SourceFile> sourceFiles = <Uri, SourceFile>{};
   int dartCharactersRead = 0;
 
-  Future<String> readStringFromUri(Uri resourceUri) {
-    return readUtf8BytesFromUri(resourceUri).then(UTF8.decode);
-  }
-
   Future<List<int>> readUtf8BytesFromUri(Uri resourceUri) {
     if (resourceUri.scheme == 'file') {
       return _readFromFile(resourceUri);
     } else if (resourceUri.scheme == 'http' || resourceUri.scheme == 'https') {
       return _readFromHttp(resourceUri);
     } else {
       throw new ArgumentError("Unknown scheme in uri '$resourceUri'");
     }
   }
 
@@ skipping 367 matching lines @@
     if (path.startsWith('/bazel-root')) {
       path = path.substring('/bazel-root/'.length);
       for (var dir in dirs) {
         var file = dir.resolve(path);
         if (await new File.fromUri(file).exists()) {
           resolvedUri = file;
           break;
         }
       }
     }
-    var result = await readUtf8BytesFromUri(resolvedUri);
+    List<int> result = await readUtf8BytesFromUri(resolvedUri);
     sourceFiles[uri] = sourceFiles[resolvedUri];
     return result;
   }
 }