WebKit roll r60239 to r60276

BUG=none
TEST=none

TBR=tony, pkasting

Review URL: http://codereview.chromium.org/2308001

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@48372 0039d316-1c4b-4281-b951-d872f2087c98

DEPS

 vars = {
   "webkit_trunk":
   "http://svn.webkit.org/repository/webkit/trunk",
-  "webkit_revision": "60239",
+  "webkit_revision": "60276",
   "ffmpeg_revision": "47712",
   "skia_revision": "562",
   "chromium_git": "http://src.chromium.org/git",