Enable Blink's asserts for release-with-asserts builds.

We run into issues where a cl lands through Chromium's trybots and then breaks the main waterfall because of this. Chromium's trybots use release-with-asserts builds.

BUG=410916

Review URL: https://codereview.chromium.org/544773003

git-svn-id: svn://svn.chromium.org/blink/trunk@181425 bbb929c8-8fbe-4397-9dbb-9b2b20218538