Support --use-kernel in memory_compiler

pkg/front_end/lib/src/fasta/source/source_loader.dart

 // Copyright (c) 2016, 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 fasta.source_loader;
 
 import 'dart:async' show Future;
 
 import 'dart:typed_data' show Uint8List;
 
@@ skipping 80 matching lines @@
   Instrumentation instrumentation;
 
   SourceLoader(this.fileSystem, this.includeComments, KernelTarget target)
       : super(target);
 
   Future<Token> tokenize(SourceLibraryBuilder library,
       {bool suppressLexicalErrors: false}) async {
     Uri uri = library.fileUri;
     // TODO(sigmund): source-loader shouldn't check schemes, but defer to the
     // underlying file system to decide whether it is supported.
-    if (uri == null || uri.scheme != "file" && uri.scheme != "multi-root") {
+    if (uri == null ||
+        uri.scheme != "file" &&
+            uri.scheme != "multi-root" &&
+            uri.scheme != "memory") {

[Siggi Cherem (dart-lang), 2017/08/23 20:45:18]

If you don't mind, let's revert the change on this file.

I just sent https://codereview.chromium.org/3006483002/ which basically deletes
this check and delegates to the underlying filesystem to let it define what's
supported.

[Johnni Winther, 2017/08/24 06:47:54]

I thought this might provoke you to fix the issue ;)

       return deprecated_inputError(
           library.uri, -1, "Not found: ${library.uri}.");
     }
 
     // Get the library text from the cache, or read from the file system.
     List<int> bytes = sourceBytes[uri];
     if (bytes == null) {
       try {
         List<int> rawBytes = await fileSystem.entityForUri(uri).readAsBytes();
         Uint8List zeroTerminatedBytes = new Uint8List(rawBytes.length + 1);
@@ skipping 421 matching lines @@
   Expression throwCompileConstantError(Expression error) {
     return target.backendTarget.throwCompileConstantError(coreTypes, error);
   }
 
   Expression buildCompileTimeError(Message message, int offset, Uri uri) {
     String text = target.context
         .format(message.withLocation(uri, offset), Severity.error);
     return target.backendTarget.buildCompileTimeError(coreTypes, text, offset);
   }
 }