Bug 1524220 - Mark 'document.documentElement.clientHeight + 200' test case fail. r=heycam

All of failure test cases in root-margin.html will be fixed by this PR
web-platform-tests/wpt#15254 .

Differential Revision: https://phabricator.services.mozilla.com/D18760

--HG--
extra : moz-landing-system : lando

Author: Hiroyuki Ikezoe

testing/web-platform/meta/intersection-observer/root-margin.html.ini

@@ -7,6 +7,10 @@
     expected:
       if os == "android": FAIL
 
+  [document.scrollingElement.scrollTop = document.documentElement.clientHeight + 200]
+    expected:
+      if os == "android": FAIL
+
   [document.scrollingElement.scrollTop = document.documentElement.clientHeight + 300]
     expected:
       if os == "android": FAIL