Add "enable_desktop_capturer" build flag (#13133)

* Make it possible to disable a module for a renderer

* Put DesktopCapturer API under a build flag

The name is "enable_desktop_capturer".
Enabled by default.

lib/renderer/api/exports/electron.js

@@ -4,9 +4,18 @@ const moduleList = require('../module-list')
 // Import common modules.
 common.defineProperties(exports)
 
-for (const module of moduleList) {
-  Object.defineProperty(exports, module.name, {
-    enumerable: !module.private,
-    get: () => require(`../${module.file}`)
+for (const {
+        name,
+        file,
+        enabled = true,
+        private: isPrivate = false
+    } of moduleList) {
+  if (!enabled) {
+    continue
+  }
+
+  Object.defineProperty(exports, name, {
+    enumerable: !isPrivate,
+    get: () => require(`../${file}`)
   })
 }

lib/renderer/api/module-list.js

@@ -1,8 +1,15 @@
+const features = process.atomBinding('features')
+
 // Renderer side modules, please sort alphabetically.
+// A module is `enabled` if there is no explicit condition defined.
 module.exports = [
-  {name: 'desktopCapturer', file: 'desktop-capturer'},
-  {name: 'ipcRenderer', file: 'ipc-renderer'},
-  {name: 'remote', file: 'remote'},
-  {name: 'screen', file: 'screen'},
-  {name: 'webFrame', file: 'web-frame'}
+  {
+    name: 'desktopCapturer',
+    file: 'desktop-capturer',
+    enabled: features.isDesktopCapturerEnabled()
+  },
+  {name: 'ipcRenderer', file: 'ipc-renderer', enabled: true},
+  {name: 'remote', file: 'remote', enabled: true},
+  {name: 'screen', file: 'screen', enabled: true},
+  {name: 'webFrame', file: 'web-frame', enabled: true}
 ]