Clarify comment
diff --git a/tools/wptrunner/wptrunner/executors/executorselenium.py b/tools/wptrunner/wptrunner/executors/executorselenium.py
index 731d07b..0675461 100644
--- a/tools/wptrunner/wptrunner/executors/executorselenium.py
+++ b/tools/wptrunner/wptrunner/executors/executorselenium.py
@@ -96,7 +96,8 @@
def get_test_window(self, window_id, parent):
test_window = None
try:
- # Try this, it's in Level 1 but nothing supports it yet
+ # Try using the JSON serialization of the WindowProxy object,
+ # it's in Level 1 but nothing supports it yet
win_s = self.webdriver.execute_script("return window['%s'];" % window_id)
win_obj = json.loads(win_s)
test_window = win_obj["window-fcc6-11e5-b4f8-330a88ab9d7f"]
