Bug 534762. Fix problem using --test-path on win32

testing/mochitest/harness-overlay.xul

@@ -42,12 +42,26 @@
       if ("testPath" in params && params.testPath) {
         var extraPath = params.testPath;
         var pathToCheck = chromeDir.clone().QueryInterface(Ci.nsILocalFile);
-        pathToCheck.appendRelativePath(extraPath);
-        if (pathToCheck.isDirectory()) {
-          chromeDir.appendRelativePath(extraPath);
-          url += extraPath + "/";
+        var pathIsFile = false;
+        try {
+          var pathParts = extraPath.toString().split("/");
+          for each (var part in pathParts) {
+            pathToCheck.append(part);
+          }          
+          if (pathToCheck.isDirectory()) {
+            for each (var part in pathParts) {
+              chromeDir.append(part);
+            }          
+            url += extraPath + "/";
+          }
+          else {
+            pathIsFile = true;
+          }
         }
-        else {
+        catch (e) {
+          pathIsFile = true;
+        }
+        if (pathIsFile) {
           singleTestPath = url + params.testPath;
         }
       }