Remove use of a V8 handle outside of bindings code in TimingInput.cpp.

R=alancutter@chromium.org, jochen@chromium.org

Review URL: https://codereview.chromium.org/196243010

git-svn-id: svn://svn.chromium.org/blink/trunk@169893 bbb929c8-8fbe-4397-9dbb-9b2b20218538