Use fixed sized spinner

services/web/public/coffee/ide/pdfng/directives/pdfSpinner.coffee

@@ -11,7 +11,7 @@ define [
 			add: (element) ->
 				h = element.height()
 				w = element.width()
-				size = Math.floor(0.5 * Math.min(h, w))
+				size = 64
 				spinner = $('<div class="pdfng-spinner" style="position: absolute; top: 50%; left:50%; transform: translateX(-50%) translateY(-50%);"><i class="fa fa-spinner fa-spin" style="color: #999"></i></div>')
 				spinner.css({'font-size' : size + 'px'})
 				element.append(spinner)