Console: cleaning up console-related methods on ScriptExecutionContext, first step of many.

R=mkwst@chromium.org, yurys@chromium.org

Review URL: https://codereview.chromium.org/23332010

git-svn-id: svn://svn.chromium.org/blink/trunk@156561 bbb929c8-8fbe-4397-9dbb-9b2b20218538