Remove deprecated call to 'Clear' from Source/bindings/v8/NPV8Object.cpp.

BUG=324225
R=dcarney@chromium.org

Review URL: https://codereview.chromium.org/96853002

git-svn-id: svn://svn.chromium.org/blink/trunk@162897 bbb929c8-8fbe-4397-9dbb-9b2b20218538