Disabled select element should not fire onchange event.

After http://trac.webkit.org/changeset/140286, select elements can scroll
whether they are disabled or not. While they scroll, they also change the
selected item.
This patch allows the select element to scroll, but does not change the selection if the select element is disabled.

BUG=215494
TEST=fast/forms/select/listbox-disabled-no-autoscroll.html

Review URL: https://chromiumcodereview.appspot.com/14996003

git-svn-id: svn://svn.chromium.org/blink/trunk@149951 bbb929c8-8fbe-4397-9dbb-9b2b20218538
4 files changed