Make it possible to share the embedder's dart sources for the vmservice

sdk/lib/vmservice/asset.dart

 // Copyright (c) 2015, 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.
 
 part of dart._vmservice;
 
 class Asset {
   final String name;
   final Uint8List data;
 
@@ skipping 41 matching lines @@
         continue;
       }
       assets[asset.name] = asset;
     }
     return assets;
   }
 
   String toString() => '$name ($mimeType)';
 }
 
+HashMap<String, Asset> _assets;
+HashMap<String, Asset> get assets {
+  if (_assets == null) {
+    try {
+      _assets = Asset.request();
+    } catch (e) {
+      print('Could not load Observatory assets: $e');
+    }
+  }
+  return _assets;
+}
 
 class _ByteStream {
   final Uint8List bytes;
   final int offset;
   int get length => bytes.length - offset;
   int _cursor = 0;
 
   _ByteStream(this.bytes, [this.offset = 0]);
 
   void reset() {
@@ skipping 124 matching lines @@
     int type = _readType(_bs);
     _bs.seekToNextBlock(tarHeaderSize);
     if (type != tarHeaderFileType) {
       _skipContents(_bs, size);
       return null;
     }
     Uint8List bytes = _readContents(_bs, size);
     return new Asset(filename, bytes);
   }
 }