Add readAsStringSync() to File.

pkg/analyzer/lib/file_system/memory_file_system.dart

 // Copyright (c) 2014, 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 memory_file_system;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:analyzer/src/generated/engine.dart' show TimestampedData;
@@ skipping 188 matching lines @@
 
   @override
   Source createSource([Uri uri]) {
     throw new FileSystemException(path, 'File could not be read');
   }
 
   @override
   bool isOrContains(String path) {
     return path == this.path;
   }
+
+  @override
+  String readAsStringSync() {
+    throw new FileSystemException(path, 'File could not be read');
+  }
 }
 
 /**
  * An in-memory implementation of [File].
  */
 class _MemoryFile extends _MemoryResource implements File {
   _MemoryFile(MemoryResourceProvider provider, String path)
       : super(provider, path);
 
   @override
   bool get exists => _provider._pathToResource[path] is _MemoryFile;
 
   int get modificationStamp {
     int stamp = _provider._pathToTimestamp[path];
     if (stamp == null) {
-      throw new FileSystemException(path, 'File does not exist.');
+      throw new FileSystemException(path, 'File "$path" does not exist.');
     }
     return stamp;
   }
 
   String get _content {
     String content = _provider._pathToContent[path];
     if (content == null) {
-      throw new FileSystemException(path, "File does not exist");
+      throw new FileSystemException(path, 'File "$path" does not exist.');
     }
     return content;
   }
 
   @override
   Source createSource([Uri uri]) {
     if (uri == null) {
       uri = posix.toUri(path);
     }
     return new _MemoryFileSource(this, uri);
   }
 
   @override
   bool isOrContains(String path) {
     return path == this.path;
   }
+
+  @override
+  String readAsStringSync() {
+    String content = _provider._pathToContent[path];
+    if (content == null) {
+      throw new FileSystemException(path, 'File "$path" does not exist.');
+    }
+    return content;
+  }
 }
 
 /**
  * An in-memory implementation of [Source].
  */
 class _MemoryFileSource extends Source {
   /**
    * Map from encoded URI/filepath pair to a unique integer identifier.  This
    * identifier is used for equality tests and hash codes.
    *
@@ skipping 188 matching lines @@
   bool operator ==(other) {
     if (runtimeType != other.runtimeType) {
       return false;
     }
     return path == other.path;
   }
 
   @override
   String toString() => path;
 }