spec: add test for syncronous access to blink APIs (#14637)

This test should ensure we catch a regression of #13787

spec/fixtures/module/access-blink-apis.js

@@ -0,0 +1,17 @@
+window.delayed = true
+
+global.getGlobalNames = () => {
+  return Object.getOwnPropertyNames(global)
+    .filter(key => typeof global[key] === 'function')
+    .filter(key => key !== 'WebView')
+    .sort()
+}
+
+const atPreload = global.getGlobalNames()
+
+window.addEventListener('load', () => {
+  window.test = {
+    atPreload,
+    atLoad: global.getGlobalNames()
+  }
+})