Postpone the scanning

... to the point when the panel is already ready.

Hopefully, this makes the sidebar connect and appear sooner.

We can't delay in any further, because setting the
visible highlights (which happens in the next line)
will trigger a bucket bar (a.k.a. heatmap) refresh,
and the heatmap uses information produced by the scanning.

h/static/scripts/host.coffee

@@ -40,6 +40,7 @@ class Annotator.Host extends Annotator.Guest
     # Host frame dictates the toolbar options.
     this.on 'panelReady', =>
       this.setTool('comment')
+      this._scan() # Scan the document
       this.setVisibleHighlights(!!options.showHighlights)
 
     if @plugins.BucketBar?
@@ -48,9 +49,6 @@ class Annotator.Host extends Annotator.Guest
         if @frame.hasClass 'annotator-collapsed'
           this.showFrame()
 
-    # Scan the document
-    this._scan()
-
   actuallyShowFrame: (options={transition: true}) ->
     unless @drag.enabled
       @frame.css 'margin-left': "#{-1 * @frame.width()}px"