Add a WebLockOrientationError independant from WebLockOrientationCallback.

So we don't need to include WebLockOrientationCallback in places where
we should only include enums.

BUG=162827
NOTRY=true

Review URL: https://codereview.chromium.org/332493003

git-svn-id: svn://svn.chromium.org/blink/trunk@176510 bbb929c8-8fbe-4397-9dbb-9b2b20218538