add sigterm handling to wptrunner (#37591)

* rebase

* fix handler name

tools/wptrunner/wptrunner/wptrunner.py

@@ -2,6 +2,7 @@
 
 import json
 import os
+import signal
 import sys
 from collections import defaultdict
 from datetime import datetime, timedelta
@@ -257,6 +258,7 @@ def run_test_iteration(test_status, test_loader, test_source_kwargs, test_source
                           run_test_kwargs["restart_on_new_group"],
                           recording=recording) as manager_group:
             try:
+                handle_interrupt_signals()
                 manager_group.run(tests_to_run)
             except KeyboardInterrupt:
                 logger.critical("Main thread got signal")
@@ -274,6 +276,14 @@ def run_test_iteration(test_status, test_loader, test_source_kwargs, test_source
 
     return True
 
+def handle_interrupt_signals():
+    def termination_handler(_signum, _unused_frame):
+        raise KeyboardInterrupt()
+    if sys.platform == "win32":
+        signal.signal(signal.SIGBREAK, termination_handler)
+    else:
+        signal.signal(signal.SIGTERM, termination_handler)
+
 
 def evaluate_runs(test_status, run_test_kwargs):
     """Evaluates the test counts after the given number of repeat runs has finished"""