Make methods in URLUtils and URLUtilsReadOnly nonstatic

No behavior changes: decrufting, initial trial CL for bug
Issue 360435: Web IDL: make 'implements' use (object) methods, not static member functions
https://code.google.com/p/chromium/issues/detail?id=360435

Currently the methods in URLUtils and URLUtilsReadOnly are static,
due to considering |implements| in Web IDL as meaning "interface extension",
as is done for partial interfaces.
However, |implements| actually corresponds to *multiple inheritance*,
and in fact Blink classes implementing interfaces that (IDL) implement
URLUtils and URLUtilsReadOnly (C++) inherit the classes URLUtils or
URLUtilsReadOnly.
Thus the |static| and explicit passing of |impl| as an argument are just
cruft; this CL removes them.

Also:
* renames local variable |url| => |kurl| to avoid name collision
* cleanup IDL files (comments esp.)

R=haraken
BUG=360435

Review URL: https://codereview.chromium.org/225263003

git-svn-id: svn://svn.chromium.org/blink/trunk@170948 bbb929c8-8fbe-4397-9dbb-9b2b20218538