Remove the compile time flag for DATALIST Element.

This is part of work for cleaning up #ifdefs from Blink source to reduce complexity.
    DATALIST Element is always Enabled on the chromium side.
    A separate patch ( https://codereview.chromium.org/14861002) will disable them on Android platform.

BUG=

Review URL: https://chromiumcodereview.appspot.com/14859003

git-svn-id: svn://svn.chromium.org/blink/trunk@150903 bbb929c8-8fbe-4397-9dbb-9b2b20218538
32 files changed