feat: [extensions] background pages (#21591)

spec-main/fixtures/extensions/lazy-background-page/background.js

@@ -0,0 +1,4 @@
+/* eslint-disable no-undef */
+chrome.runtime.onMessage.addListener((message, sender, reply) => {
+  reply({ message, sender })
+})

spec-main/fixtures/extensions/lazy-background-page/content_script.js

@@ -0,0 +1,6 @@
+/* eslint-disable no-undef */
+chrome.runtime.sendMessage({ some: 'message' }, (response) => {
+  const script = document.createElement('script')
+  script.textContent = `require('electron').ipcRenderer.send('bg-page-message-response', ${JSON.stringify(response)})`
+  document.documentElement.appendChild(script)
+})

spec-main/fixtures/extensions/lazy-background-page/manifest.json

@@ -0,0 +1,16 @@
+{
+  "name": "lazy-background-page",
+  "version": "1.0",
+  "background": {
+    "scripts": ["background.js"],
+    "persistent": false
+  },
+  "content_scripts": [
+    {
+      "matches": ["<all_urls>"],
+      "js": ["content_script.js"],
+      "run_at": "document_start"
+    }
+  ],
+  "manifest_version": 2
+}