Flaky on Mac10.13: external/wpt/domxpath/xml_xpath_runner.html.

TBR=dcheng@chromium.org

Bug: 907412
Change-Id: I903923a922f8116841e9260aa715eeaaf896549b
Reviewed-on: https://chromium-review.googlesource.com/c/1346450
Commit-Queue: Anders Ruud <andruud@chromium.org>
Reviewed-by: Anders Ruud <andruud@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610045}

third_party/WebKit/LayoutTests/TestExpectations

@@ -5360,3 +5360,4 @@ crbug.com/906952 fast/events/before-unload-return-value-from-listener.html [ Pas
 
 # See also crbug.com/907150
 crbug.com/667560 http/tests/devtools/console-cross-origin-iframe-logging.js [ Pass Failure Timeout ]
+crbug.com/907412 [ Mac10.13 ] external/wpt/domxpath/xml_xpath_runner.html [ Pass Timeout ]