debug: connect after child is ready

We now wait to connect to the debuggee until we know that its error
stream has data, to ensure that the output message "connecting..... ok"
appears after "Debugger listening on port xyz"

I also increased the test timeout to let the more complex tests finish
in time on Windows

This change fixes the following unit tests on Windows:
 test-debugger-repl.js
 test-debugger-repl-term.js
 test-debugger-repl-utf8.js
 test-debugger-repl-restart.js

lib/_debugger.js

@@ -25,6 +25,7 @@ var util = require('util'),
     vm = require('vm'),
     repl = require('repl'),
     inherits = util.inherits,
+    assert = require('assert'),
     spawn = require('child_process').spawn;
 
 exports.start = function(argv, stdin, stdout) {
@@ -1612,6 +1613,7 @@ Interface.prototype.trySpawn = function(cb) {
       childArgs = this.args;
 
   this.killChild();
+  assert(!this.child);
 
   if (this.args.length === 2) {
     var match = this.args[1].match(/^([^:]+):(\d+)$/);
@@ -1647,12 +1649,10 @@ Interface.prototype.trySpawn = function(cb) {
     }
   }
 
-  if (!this.child) {
-    this.child = spawn(process.execPath, childArgs);
+  this.child = spawn(process.execPath, childArgs);
 
-    this.child.stdout.on('data', this.childPrint.bind(this));
-    this.child.stderr.on('data', this.childPrint.bind(this));
-  }
+  this.child.stdout.on('data', this.childPrint.bind(this));
+  this.child.stderr.on('data', this.childPrint.bind(this));
 
   this.pause();
 
@@ -1709,8 +1709,10 @@ Interface.prototype.trySpawn = function(cb) {
     client.connect(port, host);
   }
 
-  setTimeout(function() {
-    self.print('connecting to port ' + port + '..', true);
-    attemptConnect();
-  }, 50);
+  this.child.stderr.once('data', function() {
+    setImmediate(function() {
+      self.print('connecting to port ' + port + '..', true);
+      attemptConnect();
+    });
+  });
 };

test/simple/helper-debugger-repl.js

@@ -91,7 +91,7 @@ function startDebugger(scriptToDebug) {
     });
 
     quit();
-  }, 5000).unref();
+  }, 10000).unref();
 
   process.once('uncaughtException', function(e) {
     console.error('UncaughtException', e, e.stack);