Check target of keyEvent instead of activeElement for text editability

inject.js

@@ -364,9 +364,9 @@
           }
 
           // Ignore keydown event if typing in an input box
-          if (document.activeElement.nodeName === 'INPUT'
-              || document.activeElement.nodeName === 'TEXTAREA'
-              || document.activeElement.isContentEditable) {
+          if (event.target.nodeName === 'INPUT'
+              || event.target.nodeName === 'TEXTAREA'
+              || event.target.isContentEditable) {
             return false;
           }