Update WebTestProxy::createColorChooser to prevent hidden virtual function warning

Updating WebTestProxy::createColorChooser to the method with the extra argument
to avoid the "hides overloaded virtual function" warning.

BUG=None

Review URL: https://codereview.chromium.org/80933002

git-svn-id: svn://svn.chromium.org/blink/trunk@162536 bbb929c8-8fbe-4397-9dbb-9b2b20218538