Bug 1557463 [wpt PR 17212] - Add mandatory capabilities parameter for webdriver new session command, a=testonly

Automatic update from web-platform-tests
Add mandatory capabilities parameter in the body for the webdriver new session command (#17212)

--

wpt-commits: 693543f7296ef79cc4ec534422c5a0bb433992dd
wpt-pr: 17212

testing/web-platform/tests/tools/webdriver/webdriver/client.py

@@ -413,7 +413,7 @@ class Session(object):
         if self.session_id is not None:
             return
 
-        body = {}
+        body = {"capabilities": {}}
 
         if self.requested_capabilities is not None:
             body["capabilities"] = self.requested_capabilities