[chromium] Enable ChromeDriver log for WPT tests

Enable chromedriver log for CI wpt tests

Change-Id: I02d4acb627ca90233b7c0dab401c7c28e6759604
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2402319Reviewed-by: John Chen <johnchen@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Shengfa Lin <shengfa@google.com>
Cr-Commit-Position: refs/heads/master@{#805817}

testing/buildbot/gn_isolate_map.pyl

@@ -519,6 +519,7 @@
       "../../chrome/test/chromedriver/test/run_webdriver_tests.py",
       "-v",
       "--chromedriver=chromedriver",
+      "--log-path=${ISOLATED_OUTDIR}/chromedriver.log",
       "--output-dir=${ISOLATED_OUTDIR}",
       "--test-path=../../third_party/blink/web_tests/external/wpt/webdriver/tests/",
     ],