feat: preloads and nodeIntegration in iframes (#16425)

* feat: add support for node / preloads in subframes

This feature has delibrately been built / implemented in such a way
that it has minimum impact on existing apps / code-paths.
Without enabling the new "nodeSupportInSubFrames" option basically none of this
new code will be hit.

The things that I believe need extra scrutiny are:

* Introduction of `event.reply` for IPC events and usage of `event.reply` instead of `event.sender.send()`
* Usage of `node::FreeEnvironment(env)` when the new option is enabled in order to avoid memory leaks.  I have tested this quite a bit and haven't managed to cause a crash but it is still feature flagged behind the "nodeSupportInSubFrames" flag to avoid potential impact.

Closes #10569
Closes #10401
Closes #11868
Closes #12505
Closes #14035

* feat: add support preloads in subframes for sandboxed renderers

* spec: add tests for new nodeSupportInSubFrames option

* spec: fix specs for .reply and ._replyInternal for internal messages

* chore: revert change to use flag instead of environment set size

* chore: clean up subframe impl

* chore: apply suggestions from code review

Co-Authored-By: MarshallOfSound <samuel.r.attard@gmail.com>

* chore: clean up reply usage

* chore: fix TS docs generation

* chore: cleanup after rebase

* chore: rename wrap to add in event fns

lib/browser/api/web-contents.js

@@ -143,6 +143,18 @@ WebContents.prototype._sendInternalToAll = function (channel, ...args) {
 
   return this._send(internal, sendToAll, channel, args)
 }
+WebContents.prototype.sendToFrame = function (frameId, channel, ...args) {
+  if (typeof channel !== 'string') {
+    throw new Error('Missing required channel argument')
+  } else if (typeof frameId !== 'number') {
+    throw new Error('Missing required frameId argument')
+  }
+
+  const internal = false
+  const sendToAll = false
+
+  return this._sendToFrame(internal, sendToAll, frameId, channel, args)
+}
 WebContents.prototype._sendToFrameInternal = function (frameId, channel, ...args) {
   if (typeof channel !== 'string') {
     throw new Error('Missing required channel argument')
@@ -330,6 +342,22 @@ WebContents.prototype.loadFile = function (filePath, options = {}) {
   }))
 }
 
+const addReplyToEvent = (event) => {
+  event.reply = (...args) => {
+    event.sender.sendToFrame(event.frameId, ...args)
+  }
+}
+
+const addReplyInternalToEvent = (event) => {
+  Object.defineProperty(event, '_replyInternal', {
+    configurable: false,
+    enumerable: false,
+    value: (...args) => {
+      event.sender._sendToFrameInternal(event.frameId, ...args)
+    }
+  })
+}
+
 // Add JavaScript wrappers for WebContents class.
 WebContents.prototype._init = function () {
   // The navigation controller.
@@ -343,6 +371,7 @@ WebContents.prototype._init = function () {
 
   // Dispatch IPC messages to the ipc module.
   this.on('-ipc-message', function (event, [channel, ...args]) {
+    addReplyToEvent(event)
     this.emit('ipc-message', event, channel, ...args)
     ipcMain.emit(channel, event, ...args)
   })
@@ -354,11 +383,13 @@ WebContents.prototype._init = function () {
       },
       get: function () {}
     })
+    addReplyToEvent(event)
     this.emit('ipc-message-sync', event, channel, ...args)
     ipcMain.emit(channel, event, ...args)
   })
 
   this.on('ipc-internal-message', function (event, [channel, ...args]) {
+    addReplyInternalToEvent(event)
     ipcMainInternal.emit(channel, event, ...args)
   })
 
@@ -369,6 +400,7 @@ WebContents.prototype._init = function () {
       },
       get: function () {}
     })
+    addReplyInternalToEvent(event)
     ipcMainInternal.emit(channel, event, ...args)
   })