Add a trusted filter for iframe downloads (#836)

* add trusted helper to iframe downloads

services/web/app/views/project/editor/pdf.pug

@@ -305,7 +305,7 @@ div.full-size.pdf(ng-controller="PdfController")
 				dbl-click-callback="syncToCode"
 			)
 			iframe(
-				ng-src="{{ pdf.url }}"
+				ng-src="{{ pdf.url | trusted }}"
 				ng-if="settings.pdfViewer == 'native'"
 			)
 

services/web/public/coffee/ide/pdf/controllers/PdfController.coffee

@@ -12,6 +12,10 @@ define [
 	# and then again on ack.
 	AUTO_COMPILE_DEBOUNCE = 2000
 
+	App.filter('trusted', ['$sce', ($sce)->
+		return (url)-> return $sce.trustAsResourceUrl(url);
+	])
+
 	App.controller "PdfController", ($scope, $http, ide, $modal, synctex, event_tracking, logHintsFeedback, localStorage) ->
 		# enable per-user containers by default
 		perUserCompile = true