Bug 931445 - Part 5 - Avoid childIframe subtest to be started twice. r=smaug

This is a silly bug that start() is called twice in this subtest, one
from the load event of the document (by pointerlock_utils.js), the other
is by onload of the iframe. Given the document's load event comes later,
I removed the onload of iframe.

MozReview-Commit-ID: 7TQJVa3xCb9

--HG--
extra : transplant_source : %88%DFF%5E%CD%84%19%01e%A9%18%7E%85%C75%E4%BAb%EC%03

dom/tests/mochitest/pointerlock/file_childIframe.html

@@ -37,7 +37,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=633602
     <table id="childTable">
       <tr>
         <td>
-          <iframe id="iframe" src="iframe_differentDOM.html" onload="start();">
+          <iframe id="iframe" src="iframe_differentDOM.html">
           </iframe>
         </td>
         <td>

dom/tests/mochitest/pointerlock/mochitest.ini

@@ -23,4 +23,4 @@ support-files =
 
 [test_pointerlock-api.html]
 tags = fullscreen
-skip-if = buildapp == 'b2g' || toolkit == 'android' || os == 'win' # B2G - window.open focus issues using fullscreen. Win: Bug 931445
+skip-if = buildapp == 'b2g' || toolkit == 'android' # B2G - window.open focus issues using fullscreen.