Use pdf-loaded event in specs

spec/chromium-spec.js

@@ -987,7 +987,7 @@ describe('chromium feature', function () {
       w = new BrowserWindow({
         show: false,
         webPreferences: {
-          preload: path.join(fixtures, 'module', 'preload-inject-ipc.js'),
+          preload: path.join(fixtures, 'module', 'preload-pdf-loaded.js'),
           plugins: plugins
         }
       })
@@ -996,22 +996,14 @@ describe('chromium feature', function () {
     it('opens when loading a pdf resource as top level navigation', function (done) {
       createBrowserWindow({plugins: true})
       ipcMain.once('pdf-loaded', function (event, success) {
-        if (success) done()
+        success ? done() : done(new Error(`Unexpected loading state: ${success}`))
       })
       w.webContents.on('page-title-updated', function () {
-        const source = `
-          if (window.viewer) {
-            window.viewer.setLoadCallback(function(success) {
-              window.ipcRenderer.send('pdf-loaded', success);
-            });
-          }
-        `
         const parsedURL = url.parse(w.webContents.getURL(), true)
         assert.equal(parsedURL.protocol, 'chrome:')
         assert.equal(parsedURL.hostname, 'pdf-viewer')
         assert.equal(parsedURL.query.src, pdfSource)
         assert.equal(w.webContents.getTitle(), 'cat.pdf')
-        w.webContents.executeJavaScript(source)
       })
       w.webContents.loadURL(pdfSource)
     })

spec/fixtures/module/preload-pdf-loaded.js

@@ -0,0 +1,5 @@
+const {ipcRenderer} = require('electron')
+
+window.addEventListener('pdf-loaded', function (event) {
+  ipcRenderer.send('pdf-loaded', event.detail);
+})