feat: emit process 'loaded' event in sandboxed renderers (#17680)

lib/sandboxed_renderer/init.js

@@ -56,6 +56,9 @@ v8Util.setHiddenValue(global, 'ipcNative', {
 
 // AtomSandboxedRendererClient will look for the "lifecycle" hidden object when
 v8Util.setHiddenValue(global, 'lifecycle', {
+  onLoaded () {
+    process.emit('loaded')
+  },
   onExit () {
     process.emit('exit')
   },
@@ -89,6 +92,7 @@ Object.defineProperty(preloadProcess, 'noDeprecation', {
   }
 })
 
+process.on('loaded', () => preloadProcess.emit('loaded'))
 process.on('exit', () => preloadProcess.emit('exit'))
 
 // This is the `require` function that will be visible to the preload script