Load time improvements (fixes #140)

lib/devc.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.
 
 /// Command line tool to run the checker on a Dart program.
 library dev_compiler.devc;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
@@ skipping 272 matching lines @@
   }
 
   shelf.Handler rebuildAndCache(shelf.Handler handler) => (request) {
     _log.fine('requested $GREEN_COLOR${request.url}$NO_COLOR');
     // Trigger recompile only when requesting the HTML page.
     var segments = request.url.pathSegments;
     bool isEntryPage = segments.length == 0 || segments[0] == _entryPath;
     if (isEntryPage) compiler._runAgain();
 
     // To help browsers cache resources that don't change, we serve these
-    // resources under a path containing their hash:
-    //    /cached/{hash}/{path-to-file.js}
-    bool isCached = segments.length > 1 && segments[0] == 'cached';
-    if (isCached) {
-      // Changing the request lets us record that the hash prefix is handled
-      // here, and that the underlying handler should use the rest of the url to
-      // determine where to find the resource in the file system.
-      request = request.change(path: path.join('cached', segments[1]));
-    }
+    // resources by adding a query parameter containing their hash:
+    //    /{path-to-file.js}?____cached={hash}
+    var hash = request.url.queryParameters['____cached'];
     var response = handler(request);
-    var policy = isCached ? 'max-age=${24 * 60 * 60}' : 'no-cache';
+    var policy = hash != null ? 'max-age=${24 * 60 * 60}' : 'no-cache';
     var headers = {'cache-control': policy};
-    if (isCached) {
+    if (hash != null) {
       // Note: the cache-control header should be enough, but this doesn't hurt
       // and can help renew the policy after it expires.
-      headers['ETag'] = segments[1];
+      headers['ETag'] = hash;
     }
     return response.change(headers: headers);
   };
 }
 
 final _log = new Logger('dev_compiler');
 final _earlyErrorResult = new CheckerResults(const [], null, true);