Remove password generation from Blink.

This feature is now implemented entirely in Chromium
(http://crbug.com/114092) and this is now dead code.

Resolves FIXME left 10 months ago in
https://chromiumcodereview.appspot.com/18414005

Review URL: https://codereview.chromium.org/289153002

git-svn-id: svn://svn.chromium.org/blink/trunk@174547 bbb929c8-8fbe-4397-9dbb-9b2b20218538