Don't include Cache-Control header for served assets.

lib/src/barback/barback_server.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.
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 
 import 'package:barback/barback.dart';
 import "package:crypto/crypto.dart";
@@ skipping 154 matching lines @@
       // Allow the asset to be cached based on its content hash.
       var sha = new SHA1();
       await hashStream.forEach((chunk) {
         sha.add(chunk);
       });
 
       var assetSha = BASE64.encode(sha.close());
       var previousSha = request.headers["if-none-match"];
 
       var headers = {
-        // Enabled browser caching of the asset.
-        "Cache-Control": "max-age=3600",
+        // Enable browser caching of the asset.
         "ETag": assetSha
       };
 
       if (assetSha == previousSha) {
         // We're requesting an unchanged asset so don't push its body down the
         // wire again.
         addResult(new BarbackServerResult._cached(request.url, asset.id));
         return new shelf.Response.notModified(headers: headers);
       } else {
         addResult(new BarbackServerResult._success(request.url, asset.id));
@@ skipping 49 matching lines @@
       : error = null,
         isCached = false;
 
   BarbackServerResult._cached(this.url, this.id)
       : error = null,
         isCached = true;
 
   BarbackServerResult._failure(this.url, this.id, this.error)
       : isCached = false;
 }