Load time improvements (fixes #140):

- move hash to a query parameter (it works!)
- do widget request later, let app render/loading in case the request is fast
enough.

[email protected]

Review URL: https://codereview.chromium.org/1131933003

Author: sigmundch

pkg/dev_compiler/lib/devc.dart

@@ -290,22 +290,16 @@ class CompilerServer {
     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);
   };

pkg/dev_compiler/lib/runtime/messages_widget.dart

@@ -15,7 +15,10 @@ import 'package:path/path.dart' as path;
 import 'package:source_span/source_span.dart';
 import 'package:dev_compiler/src/summary.dart';
 
-main() async => displayMessages(await HttpRequest.getString('messages.json'));
+main() async {
+  await window.animationFrame;
+  displayMessages(await HttpRequest.getString('messages.json'));
+}
 
 void displayMessages(String data) {
   var summary = GlobalSummary.parse(JSON.decode(data));