--- a/browser/extensions/pdfjs/test/browser_pdfjs_main.js
+++ b/browser/extensions/pdfjs/test/browser_pdfjs_main.js
@@ -16,17 +16,16 @@ add_task(async function test() {
 
   await BrowserTestUtils.withNewTab({ gBrowser, url: "about:blank" },
     async function(newTabBrowser) {
       await waitForPdfJS(newTabBrowser, TESTROOT + "file_pdfjs_test.pdf");
 
       await ContentTask.spawn(newTabBrowser, null, async function() {
         // Overall sanity tests
         Assert.ok(content.document.querySelector("div#viewer"), "document content has viewer UI");
-        Assert.ok("PDFJS" in content.wrappedJSObject, "window content has PDFJS object");
 
         // Sidebar: open
         var sidebar = content.document.querySelector("button#sidebarToggle"),
             outerContainer = content.document.querySelector("div#outerContainer");
 
         sidebar.click();
         Assert.ok(outerContainer.classList.contains("sidebarOpen"), "sidebar opens on click");
 

--- a/browser/extensions/pdfjs/test/browser_pdfjs_navigation.js
+++ b/browser/extensions/pdfjs/test/browser_pdfjs_navigation.js
@@ -153,17 +153,16 @@ add_task(async function test() {
 
   await BrowserTestUtils.withNewTab({ gBrowser, url: "about:blank" },
     async function(newTabBrowser) {
       await waitForPdfJS(newTabBrowser, TESTROOT + "file_pdfjs_test.pdf");
 
       await ContentTask.spawn(newTabBrowser, null, async function() {
         // Check if PDF is opened with internal viewer
         Assert.ok(content.document.querySelector("div#viewer"), "document content has viewer UI");
-        Assert.ok("PDFJS" in content.wrappedJSObject, "window content has PDFJS object");
       });
 
       await ContentTask.spawn(newTabBrowser, null, contentSetUp);
 
       await runTests(newTabBrowser);
 
       await ContentTask.spawn(newTabBrowser, null, async function() {
         let pageNumber = content.document.querySelector("input#pageNumber");

--- a/browser/extensions/pdfjs/test/browser_pdfjs_views.js
+++ b/browser/extensions/pdfjs/test/browser_pdfjs_views.js
@@ -16,17 +16,16 @@ add_task(async function test() {
 
   await BrowserTestUtils.withNewTab({ gBrowser, url: "about:blank" },
     async function(browser) {
       // check that PDF is opened with internal viewer
       await waitForPdfJS(browser, TESTROOT + "file_pdfjs_test.pdf");
 
       await ContentTask.spawn(browser, null, async function() {
         Assert.ok(content.document.querySelector("div#viewer"), "document content has viewer UI");
-        Assert.ok("PDFJS" in content.wrappedJSObject, "window content has PDFJS object");
 
         // open sidebar
         var sidebar = content.document.querySelector("button#sidebarToggle");
         var outerContainer = content.document.querySelector("div#outerContainer");
 
         sidebar.click();
         Assert.ok(outerContainer.classList.contains("sidebarOpen"), "sidebar opens on click");
 

--- a/browser/extensions/pdfjs/test/browser_pdfjs_zoom.js
+++ b/browser/extensions/pdfjs/test/browser_pdfjs_zoom.js
@@ -86,17 +86,16 @@ add_task(async function test() {
               document.removeEventListener("pagerendered", onPageRendered, true);
               resolve();
             }, true);
           });
         }
 
         // check that PDF is opened with internal viewer
         Assert.ok(content.document.querySelector("div#viewer"), "document content has viewer UI");
-        Assert.ok("PDFJS" in content.wrappedJSObject, "window content has PDFJS object");
 
         let initialWidth, previousWidth;
         initialWidth = previousWidth =
           parseInt(content.document.querySelector("div.page[data-page-number='1']").style.width);
 
         for (let subTest of contentTESTS) {
           // We zoom using an UI element
           var ev;