Bug 897849 - Debugger should use { showArrows: true } when initializing the SideMenuWidget; r=vporof

browser/devtools/debugger/debugger-panes.js

@@ -36,7 +36,8 @@ SourcesView.prototype = Heritage.extend(WidgetMethods, {
     dumpn("Initializing the SourcesView");
 
     this.widget = new SideMenuWidget(document.getElementById("sources"), {
-      showCheckboxes: true
+      showCheckboxes: true,
+      showArrows: true
     });
     this.emptyText = L10N.getStr("noSourcesText");
     this.unavailableText = L10N.getStr("noMatchingSourcesText");