Avoid cache when deprecating document.all

To deprecate document.all, simply changing its getter and setter would
activate its cache mechanism, and degrade the performance. Here we
assign it first to 'undefined' to avoid this.

BUG=https://code.google.com/p/chromium/issues/detail?id=239756

Review URL: https://chromiumcodereview.appspot.com/16118002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@204493 0039d316-1c4b-4281-b951-d872f2087c98
1 file changed