Replace remote module with invoke calls.

The remote module has been deprecated and is set to be removed on electron version 11.
We have two options to replace the remote module

1. use @electron/remote module
2. Send messages using send/invoke.

I am using invoke since it is the
[recommended](https://www.npmjs.com/package/@electron/remote) option to use.

src/main-process/atom-application.js

@@ -133,6 +133,13 @@ const decryptOptions = (optionsMessage, secret) => {
   return JSON.parse(message);
 };
 
+ipcMain.handle('isDefaultProtocolClient', (_, { protocol, path, args }) => {
+  return app.isDefaultProtocolClient(protocol, path, args);
+});
+
+ipcMain.handle('setAsDefaultProtocolClient', (_, { protocol, path, args }) => {
+  return app.setAsDefaultProtocolClient(protocol, path, args);
+});
 // The application's singleton class.
 //
 // It's the entry point into the Atom application and maintains the global state

src/protocol-handler-installer.js

@@ -1,4 +1,4 @@
-const { remote } = require('electron');
+const { ipcRenderer } = require('electron');
 
 const SETTING = 'core.uriHandlerRegistration';
 const PROMPT = 'prompt';
@@ -10,26 +10,28 @@ module.exports = class ProtocolHandlerInstaller {
     return ['win32', 'darwin'].includes(process.platform);
   }
 
-  isDefaultProtocolClient() {
-    return remote.app.isDefaultProtocolClient('atom', process.execPath, [
-      '--uri-handler',
-      '--'
-    ]);
+  async isDefaultProtocolClient() {
+    return ipcRenderer.invoke('isDefaultProtocolClient', {
+      protocol: 'atom',
+      path: process.execPath,
+      args: ['--uri-handler', '--']
+    });
   }
 
-  setAsDefaultProtocolClient() {
+  async setAsDefaultProtocolClient() {
     // This Electron API is only available on Windows and macOS. There might be some
     // hacks to make it work on Linux; see https://github.com/electron/electron/issues/6440
     return (
       this.isSupported() &&
-      remote.app.setAsDefaultProtocolClient('atom', process.execPath, [
-        '--uri-handler',
-        '--'
-      ])
+      ipcRenderer.invoke('setAsDefaultProtocolClient', {
+        protocol: 'atom',
+        path: process.execPath,
+        args: ['--uri-handler', '--']
+      })
     );
   }
 
-  initialize(config, notifications) {
+  async initialize(config, notifications) {
     if (!this.isSupported()) {
       return;
     }
@@ -37,12 +39,12 @@ module.exports = class ProtocolHandlerInstaller {
     const behaviorWhenNotProtocolClient = config.get(SETTING);
     switch (behaviorWhenNotProtocolClient) {
       case PROMPT:
-        if (!this.isDefaultProtocolClient()) {
+        if (await !this.isDefaultProtocolClient()) {
           this.promptToBecomeProtocolClient(config, notifications);
         }
         break;
       case ALWAYS:
-        if (!this.isDefaultProtocolClient()) {
+        if (await !this.isDefaultProtocolClient()) {
           this.setAsDefaultProtocolClient();
         }
         break;