Remove |name| parameters from DOM attribute getters/setters

When moving DOM attributes to prototype chains, we are planning to
drop |name| parameters because |name| is unused in almost all getters/setters.
In preparation for the change, this CL removes |name| parameters
from existing getters/setters.

Review URL: https://codereview.chromium.org/54523003

git-svn-id: svn://svn.chromium.org/blink/trunk@161053 bbb929c8-8fbe-4397-9dbb-9b2b20218538