Remove unnecessary NodeFilterCondition.cpp file

Remove unnecessary NodeFilterCondition.cpp file. It only contains the
implementation for acceptNode() virtual function but this one is marked
as pure virtual in the header.

R=rob.buis@samsung.com, adamk@chromium.org

Review URL: https://codereview.chromium.org/483843003

git-svn-id: svn://svn.chromium.org/blink/trunk@180494 bbb929c8-8fbe-4397-9dbb-9b2b20218538