use sync zoom api with guest view manager webpreferences

lib/browser/guest-view-manager.js

@@ -184,6 +184,7 @@ const attachGuest = function (event, elementInstanceId, guestInstanceId, params)
     guestInstanceId: guestInstanceId,
     nodeIntegration: params.nodeintegration != null ? params.nodeintegration : false,
     plugins: params.plugins,
+    zoomFactor: embedder._getZoomFactor(),
     webSecurity: !params.disablewebsecurity,
     blinkFeatures: params.blinkfeatures,
     disableBlinkFeatures: params.disableblinkfeatures
@@ -212,18 +213,15 @@ const attachGuest = function (event, elementInstanceId, guestInstanceId, params)
     return
   }
 
-  embedder.getZoomFactor(function (zoomFactor) {
-    webPreferences.zoomFactor = zoomFactor
-    webViewManager.addGuest(guestInstanceId, elementInstanceId, embedder, guest, webPreferences)
-    guest.attachParams = params
-    embedderElementsMap[key] = guestInstanceId
+  webViewManager.addGuest(guestInstanceId, elementInstanceId, embedder, guest, webPreferences)
+  guest.attachParams = params
+  embedderElementsMap[key] = guestInstanceId
 
-    guest.setEmbedder(embedder)
-    guestInstance.embedder = embedder
-    guestInstance.elementInstanceId = elementInstanceId
+  guest.setEmbedder(embedder)
+  guestInstance.embedder = embedder
+  guestInstance.elementInstanceId = elementInstanceId
 
-    watchEmbedder(embedder)
-  })
+  watchEmbedder(embedder)
 }
 
 // Destroy an existing guest instance.