Debug wpt test under lldb

[sagudev]

I am currently patching --rr-chaos with:

diff --git a/python/wpt/run.py b/python/wpt/run.py
index e994413107..5761acbe59 100644
--- a/python/wpt/run.py
+++ b/python/wpt/run.py
@@ -77,10 +77,8 @@ def run_tests(default_binary_path: str, **kwargs):
     set_if_none(kwargs, "webdriver_binary", default_binary_path)
 
     if kwargs.pop("rr_chaos"):
-        kwargs["debugger"] = "rr"
-        kwargs["debugger_args"] = "record --chaos"
-        kwargs["repeat_until_unexpected"] = True
-        # TODO: Delete rr traces from green test runs?
+        kwargs["debugger"] = "lldb"
+        kwargs["debugger_args"] = "--batch --ex run --ex bt"
 
     prefs = kwargs.pop("prefs")
     kwargs.setdefault("binary_args", [])

Ideally we would have option that would rerun crashing wpt tests under gdb/lldb automatically.