Fix: ASSERT(page->useCounter().deprecationMessage(feature).isEmpty());

It turns out that ::count and ::deprecateCount with the same 'feature' is not
supported. Due to that, r159230 caused ASSERTs to fail in many layout tests.

This CL removes the UseCounter::count part of the logic above, with the rationale that
we are only worried about the mis-use case, that we plan to deprecate.

Console log warning is kept, and the UseCounter "feature" is enabled to reflect its
purpose.

R=jchaffraix@chromium.org, Julien Chaffraix

Committed on behalf of a1.gomes@sisa.samsung.com.

Review URL: https://codereview.chromium.org/26303005

git-svn-id: svn://svn.chromium.org/blink/trunk@159271 bbb929c8-8fbe-4397-9dbb-9b2b20218538