Issue 6507 - Inject style sheet proactively from background page

composer.postload.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-present eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 525 matching lines @@
         if (currentElement && message.remove)
         {
           // Hide the selected element itself if an added blocking
           // filter is causing it to collapse. Note that this
           // behavior is incomplete, but the best we can do here,
           // e.g. if an added blocking filter matches other elements,
           // the effect won't be visible until the page is is reloaded.
           checkCollapse(currentElement.prisoner || currentElement);
 
           // Apply added element hiding filters.
-          elemhide.apply();
+          browser.runtime.sendMessage({type: "elemhide.needApply"});
         }
         deactivateBlockElement(!!message.popupAlreadyClosed);
         break;
       case "composer.content.clearPreviousRightClickEvent":
         if (!lastRightClickEventIsMostRecent)
           lastRightClickEvent = null;
         lastRightClickEventIsMostRecent = false;
         break;
       case "composer.content.dialogOpened":
         if (window == window.top)
@@ skipping 26 matching lines @@
 if (document instanceof HTMLDocument)
 {
   // There's a bug in Firefox that causes document_end content scripts to run
   // before document_start content scripts on extension startup. In this case
   // the ext object is undefined, we fail to initialize, and initializeComposer
   // returns false. As a workaround, try again after a timeout.
   // https://bugzilla.mozilla.org/show_bug.cgi?id=1395287
   if (!initializeComposer())
     setTimeout(initializeComposer, 2000);
 }