[Quota] Disable requestQuota operation on non-Document context

This function should be unsupported on Workers, since it needs user interaction.

BUG=381528

Review URL: https://codereview.chromium.org/319053003

git-svn-id: svn://svn.chromium.org/blink/trunk@175639 bbb929c8-8fbe-4397-9dbb-9b2b20218538