Bump nacl_revision to 4241.

BUG=none
TEST=native_client/tests with --enable-nacl

Review URL: http://codereview.chromium.org/6306015

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@72768 0039d316-1c4b-4281-b951-d872f2087c98

DEPS

@@ -7,7 +7,7 @@ vars = {
   "webkit_revision": "76718",
   "chromium_git": "http://git.chromium.org/git",
   "swig_revision": "69281",
-  "nacl_revision": "4209",
+  "nacl_revision": "4241",
   "libjingle_revision": "50",
   "libvpx_revision": "65287",
   "ffmpeg_revision": "71842",