<webview>: Don't reset allowtransparency and allowscaling between createGuest and attachGuest

chrome/test/data/extensions/platform_apps/web_view/simple/main.js

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 function CreateWebViewAndGuest(callback) {
   var webview = document.createElement('webview');
+  webview.allowtransparency = true;
+  webview.allowscaling = true;
   var onLoadStop = function(e) {
     chrome.test.sendMessage('WebViewTest.LAUNCHED');
     webview.removeEventListener('loadstop', onLoadStop);
     webview.removeEventListener('loadabort', onLoadAbort);
     callback();
   };
   webview.addEventListener('loadstop', onLoadStop);
 
   var onLoadAbort = function(e) {
     chrome.test.sendMessage('WebViewTest.FAILURE');
@@ skipping 14 matching lines @@
       e.window.attach(newwebview);
       document.body.appendChild(newwebview);
     });
 
     webview.addEventListener('loadstop', function(e) {
       chrome.test.sendMessage('WebViewTest.LOADSTOP');
     });
   });
   document.body.appendChild(webview);
 };