refactor: clean up the default app, add CSP (#13437)

* refactor: clean up the default app, add CSP

* chore: appease the linter

* refactor: make js2asar more generic, dont assume default_app as target

default_app/renderer.js

@@ -1,4 +1,5 @@
 const {remote, shell} = require('electron')
+const fs = require('fs')
 const path = require('path')
 const URL = require('url')
 const electronPath = path.relative(process.cwd(), remote.process.execPath)
@@ -20,3 +21,32 @@ document.querySelector('.chrome-version').innerText = `Chromium v${process.versi
 document.querySelector('.node-version').innerText = `Node v${process.versions.node}`
 document.querySelector('.v8-version').innerText = `v8 v${process.versions.v8}`
 document.querySelector('.command-example').innerText = `${electronPath} path-to-app`
+
+function getOcticonSvg (name) {
+  const octiconPath = path.resolve(__dirname, 'node_modules', 'octicons', 'build', 'svg', `${name}.svg`)
+  if (fs.existsSync(octiconPath)) {
+    const content = fs.readFileSync(octiconPath, 'utf8')
+    const div = document.createElement('div')
+    div.innerHTML = content
+    return div
+  }
+  return null
+}
+
+function loadSVG (element) {
+  for (const cssClass of element.classList) {
+    if (cssClass.startsWith('octicon-')) {
+      const icon = getOcticonSvg(cssClass.substr(8))
+      if (icon) {
+        icon.classList = element.classList
+        element.parentNode.insertBefore(icon, element)
+        element.remove()
+        break
+      }
+    }
+  }
+}
+
+for (const element of document.querySelectorAll('.octicon')) {
+  loadSVG(element)
+}