fixes #332 with adding keydown listener to parent (#334)

fixes #332
this adds keydown listener to parent document if there is one.
it does not use background files which uses unnecessary ram

inject.js

@@ -203,7 +203,13 @@ chrome.runtime.sendMessage({}, function(response) {
       }
     }
   }
-
+  inIframe () {
+    try {
+      return window.self !== window.top;
+    } catch (e) {
+      return true;
+    }
+  }
   function initializeNow(document) {
       // enforce init-once due to redundant callers
       if (!document.body || document.body.classList.contains('vsc-initialized')) {
@@ -220,8 +226,12 @@ chrome.runtime.sendMessage({}, function(response) {
         link.rel = 'stylesheet';
         document.head.appendChild(link);
       }
+      var docs = Array(document)
+      if(inIframe())
+        docs.push(window.top.document);
     
-      document.addEventListener('keydown', function(event) {
+      docs.forEach(function(doc) {
+        doc.addEventListener('keydown', function(event) {
           var keyCode = event.keyCode;
 
           // Ignore if following modifier is active.
@@ -261,6 +271,7 @@ chrome.runtime.sendMessage({}, function(response) {
 
           return false;
         }, true);
+      });
 
       function checkForVideo(node, parent, added) {
         if (node.nodeName === 'VIDEO') {