Push updates to browser.

dart/pkg/browser/lib/dart.js

 // 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.
 
 (function() {
 // Bootstrap support for Dart scripts on the page as this script.
 // TODO(18463): Remove user agent check. We will remove 'Dart' from there.
 if (!navigator.dartEnabled && (navigator.userAgent.indexOf('(Dart)') === -1)) {
   // TODO:
   // - Support in-browser compilation.
   // - Handle inline Dart scripts.
 
   // Fall back to compiled JS. Run through all the scripts and
   // replace them if they have a type that indicate that they source
   // in Dart code (type="application/dart").
   var scripts = document.getElementsByTagName("script");
   var length = scripts.length;
   for (var i = 0; i < length; ++i) {
     if (scripts[i].type == "application/dart") {
       // Remap foo.dart to foo.dart.js.
       if (scripts[i].src && scripts[i].src != '') {
         var script = document.createElement('script');
         script.src = scripts[i].src.replace(/\.dart(?=\?|$)/, '.dart.js');
         var parent = scripts[i].parentNode;
         // TODO(vsm): Find a solution for issue 8455 that works with more
         // than one script.
         document.currentScript = script;
         parent.replaceChild(script, scripts[i]);
+
+        // Support for incremental compilation.
+        script.onload = function (event) {
+          var script = event.target;
+          if (self.$dart_unsafe_incremental_support) {
+            new WebSocket(script.src.replace(/^http/, 'ws')).onmessage =
+              function (event) {
+                var patch = String(event.data);
+                self.$dart_unsafe_incremental_support.patch(patch);
+                script.dispatchEvent(
+                  new CustomEvent(
+                    "dart_program_updated",
+                    { bubbles: true, detail: { patch: patch } }));
+              };
+          }
+        };
       }
     }
   }
 }
 })();