Put console.time into a separate trace event category.

In rendering benchmarks we want to only capture trace events that are
required for the benchmark. console.time is used frequently, but everything
else from the 'webkit' category is not. Putting console.time into a separate
category 'webkit.console' will reduce overhead and make trace buffer overflows
less likely.

R=jamesr@chromium.org, nduca@chromium.org, tonyg@chromium.org
BUG=264308

Review URL: https://chromiumcodereview.appspot.com/23848006

git-svn-id: svn://svn.chromium.org/blink/trunk@157377 bbb929c8-8fbe-4397-9dbb-9b2b20218538