Update utils to new library syntax.

utils/apidoc/mdn/extract.dart

-#import ("dart:html");
-#import ("dart:json");
+import 'dart:html';
+import 'dart:json';
 
 // Workaround for HTML lib missing feature.
 Range newRange() {
   return document.createRange();
 }
 
 // Temporary range object to optimize performance computing client rects
 // from text nodes.
 Range _tempRange;
 // Hacks because ASYNC measurement is annoying when just writing a script.
@@ skipping 1292 matching lines @@
 }
 
 void documentLoaded(event) {
   // Load the database of expected methods and properties with an HttpRequest.
   new HttpRequest.get('${window.location}.json', (req) {
     data = JSON.parse(req.responseText);
     dbEntry = {'members': [], 'srcUrl': pageUrl};
     run();
   });
 }