fix(elementexplorer): Set script breakpoints with cross-platform safe

paths.

Fixes #4011

lib/debugger/debuggerCommons.js

@@ -1,4 +1,5 @@
 var baseDebugger = require('_debugger');
+var path = require('path');
 
 /**
  * Create a debugger client and attach to a running protractor process.
@@ -34,11 +35,13 @@ exports.attachDebugger = function(pid, opt_port) {
 
 /**
  * Set a breakpoint for evaluating REPL statements.
+ * This sets a breakpoint in Protractor's breakpointhook.js, so that we'll
+ * break after executing a command from the REPL.
  */
 exports.setEvaluateBreakpoint = function(client, cb) {
   client.setBreakpoint({
     type: 'scriptRegExp',
-    target: 'built/breakpointhook\.js', //jshint ignore:line
+    target: prepareDebuggerPath('built', 'breakpointhook.js'),
     line: 2
   }, function(err, response) {
     if (err) {
@@ -50,11 +53,18 @@ exports.setEvaluateBreakpoint = function(client, cb) {
 
 /**
  * Set a breakpoint for moving forward by one webdriver command.
+ * This sets a breakpoint in selenium-webdriver/lib/http.js, and is
+ * extremely sensitive to the selenium version. It works for
+ * selenium-webdriver 3.0.1
+ * This breaks on the following line in http.js:
+ *      let request = buildRequest(this.customCommands_, this.w3c, command);
+ * And will need to break at a similar point in future selenium-webdriver
+ * versions.
  */
 exports.setWebDriverCommandBreakpoint = function(client, cb) {
   client.setBreakpoint({
     type: 'scriptRegExp',
-    target: 'lib/http\.js', //jshint ignore:line
+    target: prepareDebuggerPath('lib', 'http.js'),
     line: 433
   }, function(err, response) {
     if (err) {
@@ -64,6 +74,15 @@ exports.setWebDriverCommandBreakpoint = function(client, cb) {
   });
 };
 
+/**
+ * Create a cross-platform friendly path for setting scriptRegExp breakpoints.
+ */
+function prepareDebuggerPath(...parts) {
+  return path.join(...parts)
+    .replace('\\', '\\\\')
+    .replace('.', '\\.');
+}
+
 /**
  * Trim excess symbols from the repl command so that it is consistent with
  * the user input.