feat(pause): allow the user to specify a port to be used for debugging

Using browser.pause(portNumber) will now start the debugger on the specified
port number.

Closes #956

lib/protractor.js

@@ -1120,8 +1120,10 @@ Protractor.prototype.debugger = function() {
  * browser.pause() in your test to enter the protractor debugger from that
  * point in the control flow.
  * Does not require changes to the command line (no need to add 'debug').
+ *
+ * @param {=number} opt_debugPort Optional port to use for the debugging process
  */
-Protractor.prototype.pause = function() {
+Protractor.prototype.pause = function(opt_debugPort) {
   // Patch in a function to help us visualize what's going on in the control
   // flow.
   webdriver.promise.ControlFlow.prototype.getControlFlowText = function() {
@@ -1171,6 +1173,10 @@ Protractor.prototype.pause = function() {
     return asString;
   };
 
+  if (opt_debugPort) {
+    process.debugPort = opt_debugPort;
+  }
+
   // Call this private function instead of sending SIGUSR1 because Windows.
   process._debugProcess(process.pid);
   var flow = webdriver.promise.controlFlow();
@@ -1179,7 +1185,7 @@ Protractor.prototype.pause = function() {
     console.log('Starting WebDriver debugger in a child process. Pause is ' +
         'still beta, please report issues at github.com/angular/protractor');
     var nodedebug = require('child_process').
-        fork(__dirname + '/wddebugger.js', ['localhost:5858']);
+        fork(__dirname + '/wddebugger.js', [process.debugPort]);
     process.on('exit', function() {
       nodedebug.kill('SIGTERM');
     });

lib/wddebugger.js

@@ -17,6 +17,9 @@ var client = new baseDebugger.Client();
 var host = 'localhost';
 var port = 5858;
 
+if (process.argv[2]) {
+  port = process.argv[2];
+}
 var debuggerRepl;
 
 var resumeReplCallback = null;