Import w3c tests for the service workers

third_party/WebKit/LayoutTests/imported/wpt/service-workers/service-worker/resources/update-recovery-worker.py

+def main(request, response):
+    # Set mode to 'init' for initial fetch.
+    mode = 'init'
+    if 'update-recovery-mode' in request.cookies:
+        mode = request.cookies['update-recovery-mode'].value
+
+    # no-cache itself to ensure the user agent finds a new version for each update.
+    headers = [('Cache-Control', 'no-cache, must-revalidate'),
+               ('Pragma', 'no-cache')]
+
+    extra_body = ''
+
+    if mode == 'init':
+        # Install a bad service worker that will break the controlled
+        # document navigation.
+        response.set_cookie('update-recovery-mode', 'bad')
+        extra_body = "addEventListener('fetch', function(e) { e.respondWith(Promise.reject()); });"
+    elif mode == 'bad':
+        # When the update tries to pull the script again, update to
+        # a worker service worker that does not break document
+        # navigation.  Serve the same script from then on.
+        response.delete_cookie('update-recovery-mode')
+
+    headers.append(('Content-Type', 'application/javascript'))
+    return headers, '%s' % (extra_body)