Bug 1557901 - disable test_streams_element_capture.html on win and mac for frequent failures r=jmaher

Differential Revision: https://phabricator.services.mozilla.com/D36430

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

dom/media/test/mochitest.ini

@@ -1189,7 +1189,7 @@ tags=msg capturestream
 skip-if = toolkit == 'android' # bug 1372457
 tags=msg capturestream
 [test_streams_element_capture.html]
-skip-if = toolkit == 'android' # bug 1372457
+skip-if = toolkit == 'android' ||  (os == 'win') || (os == 'mac') # bug 1372457 # bug 1557901 
 tags=msg capturestream
 [test_streams_element_capture_playback.html]
 skip-if = toolkit == 'android' # android(bug 1232305)