Append "Callback" to each value of enum CallbackType

Append Callback to values enum CallBackType to have more meaning
in the enum. Also, it has been renamed in specs.

Review URL: https://codereview.chromium.org/494133002

git-svn-id: svn://svn.chromium.org/blink/trunk@181013 bbb929c8-8fbe-4397-9dbb-9b2b20218538