Accept spaces before/after testharness.js output and CONSOLE output.

Some tests trigger CONSOLE output of various kind (LOG, ERROR,
etc.) for legitimate reasons so we shouldn't break those tests.

Furthermore, we are a little too pedantic with regards to whitespaces
around testharness output. Given how we get that output (ie. using
element.innerText), we should be less restrictive.

BUG=379442

Review URL: https://codereview.chromium.org/308223002

git-svn-id: svn://svn.chromium.org/blink/trunk@175272 bbb929c8-8fbe-4397-9dbb-9b2b20218538