feat: add webFrameMain.send() / webFrameMain.postMessage() (#26807)

docs/api/web-frame-main.md

@@ -101,6 +101,47 @@ Works like `executeJavaScript` but evaluates `scripts` in an isolated context.
 
 Returns `boolean` - Whether the reload was initiated successfully. Only results in `false` when the frame has no history.
 
+#### `frame.send(channel, ...args)`
+
+* `channel` String
+* `...args` any[]
+
+Send an asynchronous message to the renderer process via `channel`, along with
+arguments. Arguments will be serialized with the [Structured Clone
+Algorithm][SCA], just like [`postMessage`][], so prototype chains will not be
+included. Sending Functions, Promises, Symbols, WeakMaps, or WeakSets will
+throw an exception.
+
+The renderer process can handle the message by listening to `channel` with the
+[`ipcRenderer`](ipc-renderer.md) module.
+
+#### `frame.postMessage(channel, message, [transfer])`
+
+* `channel` String
+* `message` any
+* `transfer` MessagePortMain[] (optional)
+
+Send a message to the renderer process, optionally transferring ownership of
+zero or more [`MessagePortMain`][] objects.
+
+The transferred `MessagePortMain` objects will be available in the renderer
+process by accessing the `ports` property of the emitted event. When they
+arrive in the renderer, they will be native DOM `MessagePort` objects.
+
+For example:
+
+```js
+// Main process
+const { port1, port2 } = new MessageChannelMain()
+webContents.mainFrame.postMessage('port', { message: 'hello' }, [port1])
+
+// Renderer process
+ipcRenderer.on('port', (e, msg) => {
+  const [port] = e.ports
+  // ...
+})
+```
+
 ### Instance Properties
 
 #### `frame.url` _Readonly_