[chromedriver] Prevent touch_action_tests.html from reflowing during gestures.

BUG=chromedriver:1508
TBR=stgao@chromium.org

Review-Url: https://codereview.chromium.org/2349463002
Cr-Commit-Position: refs/heads/master@{#419027}

chrome/test/data/chromedriver/touch_action_tests.html

@@ -9,7 +9,9 @@
     <div id="target">
       Events are logged when tests touch this div.
     </div>
-    <div id="events">events: </div>
+    <!-- use "white-space:nowrap;" to prevent page reflows while swiping, see
+    https://bugs.chromium.org/p/chromedriver/issues/detail?id=1508 -->
+    <div id="events" style="white-space:nowrap;">events: </div>
     <div id="padding">
       We need some padding here so that the page is large enough to test swipe
       and scroll actions.