Wait for iframe to load before updating preview

Instead of waiting time period, which is non-deterministic on certain browsers.

Fixes #40

lib/editor.dart

@@ -65,15 +65,13 @@ class Editor {
 
   /// Update the preview layer with the current contents of the editor
   /// layer.
-  // worry about waitForAce?
   updatePreview() {
     if (this.edit_only) return;
 
     this.removePreview();
-    var iframe = this.createPreviewIframe();
 
-    var wait = new Duration(milliseconds: 100);
-    new Timer(wait, (){
+    var iframe = this.createPreviewIframe();
+    iframe.onLoad.first.then((_) {
       if (iframe.contentWindow == null) return;
 
       iframe

pubspec.yaml

@@ -1,5 +1,5 @@
 name: ice_code_editor
-version: 0.0.6
+version: 0.0.7
 description: Code Editor + Preview
 authors:
 - Chris Strom <chris@eeecomputes.com>

test/editor_test.dart

@@ -115,6 +115,7 @@ editor_tests() {
 
         var preview_ready = new Completer();
         editor.onPreviewChange.listen((e){
+          if (preview_ready.isCompleted) return;
           preview_ready.complete();
         });
         return preview_ready.future;

test/full_test.dart

@@ -220,6 +220,7 @@ full_tests() {
 
         var preview_ready = new Completer();
         editor.onPreviewChange.listen((e){
+          if (preview_ready.isCompleted) return;
           preview_ready.complete();
         });
         return preview_ready.future;