Replace applescript with https://github.com/sindresorhus/opn

Summary: This allows opening the Chrome debugger on OS X, Linux, and Windows, and succeeds the previous PR which used [browser-launcher2](https://github.com/benderjs/browser-launcher2) and included a `--dangerouslyDisableChromeDebuggerWebSecurity` option: https://github.com/facebook/react-native/pull/2406

[opn](https://github.com/sindresorhus/opn) is cross-platform and much simpler than browser-launcher2 (since we don't have to manage the opened Chrome instance; the OS will just use the default instance).
Closes https://github.com/facebook/react-native/pull/3394

Reviewed By: mkonicek

Differential Revision: D2550996

Pulled By: frantic

fb-gh-sync-id: fa4cbe55542562f30f77e0a6ab4bc53980ee13aa

getDevToolsMiddleware.js

@@ -10,9 +10,21 @@
 
 var execFile = require('child_process').execFile;
 var fs = require('fs');
+var opn = require('opn');
 var path = require('path');
 
-module.exports = function(options) {
+function getChromeAppName() {
+  switch (process.platform) {
+  case 'darwin':
+    return 'google chrome';
+  case 'win32':
+    return 'chrome';
+  default:
+    return 'google-chrome';
+  }
+}
+
+module.exports = function(options, isDebuggerConnected) {
   return function(req, res, next) {
     if (req.url === '/debugger-ui') {
       var debuggerPath = path.join(__dirname, 'debugger.html');
@@ -29,19 +41,18 @@ module.exports = function(options) {
         'If you still need this, please let us know.'
       );
     } else if (req.url === '/launch-chrome-devtools') {
+      if (isDebuggerConnected()) {
+        // Dev tools are already open; no need to open another session
+        res.end('OK');
+        return;
+      }
       var debuggerURL = 'http://localhost:' + options.port + '/debugger-ui';
-      var script = 'launchChromeDevTools.applescript';
       console.log('Launching Dev Tools...');
-      execFile(
+      opn(debuggerURL, {app: [getChromeAppName()]}, function(err) {
-        path.join(__dirname, script), [debuggerURL],
-        function(err, stdout, stderr) {
         if (err) {
-            console.log('Failed to run ' + script, err);
+          console.error('Google Chrome exited with error:', err);
         }
-          console.log(stdout);
+      });
-          console.warn(stderr);
-        }
-      );
       res.end('OK');
     } else {
       next();

launchChromeDevTools.applescript

@@ -1,47 +0,0 @@
-#!/usr/bin/env osascript
-
--- Copyright (c) 2015-present, Facebook, Inc.
--- All rights reserved.
---
--- This source code is licensed under the BSD-style license found in the
--- LICENSE file in the root directory of this source tree. An additional grant
--- of patent rights can be found in the PATENTS file in the same directory.
-
-on run argv
-  set theURL to item 1 of argv
-
-  tell application "Chrome"
-
-    if (count every window) = 0 then
-      make new window
-    end if
-
-    -- Find a tab currently running the debugger
-    set found to false
-    set theTabIndex to -1
-    repeat with theWindow in every window
-      set theTabIndex to 0
-      repeat with theTab in every tab of theWindow
-        set theTabIndex to theTabIndex + 1
-        if theTab's URL is theURL then
-          set found to true
-          exit repeat
-        end if
-      end repeat
-
-      if found then
-        exit repeat
-      end if
-    end repeat
-
-    if found then
-      set index of theWindow to 1
-      set theWindow's active tab index to theTabIndex
-    else
-      tell window 1
-        activate
-        make new tab with properties {URL:theURL}
-      end tell
-    end if
-  end tell
-end run

webSocketProxy.js

@@ -22,7 +22,7 @@ function attachToServer(server, path) {
       try {
         cn.send(JSON.stringify(message));
       } catch(e) {
-        console.warn('WARN: ' + e.message);
+        // Sometimes this call throws 'not opened'
       }
     });
   }
@@ -57,7 +57,14 @@ function attachToServer(server, path) {
     });
   });
 
-  return wss;
+  return {
+    server: wss,
+    isChromeConnected: () =>
+      clients
+        .map(ws => ws.upgradeReq.headers['user-agent'])
+        .filter(Boolean)
+        .some(userAgent => userAgent.includes('Chrome'))
+  };
 }
 
 module.exports = {