- added test runner, that takes file names and V8 flags as arguments and run scripts from passed files with passed flags in frontend context

BUG=chromium:635948
R=dgozman@chromium.org,alph@chromium.org

Committed: https://crrev.com/f3f9f4448dfa533d768878245a9bdbb57b4d941b
Review-Url: https://codereview.chromium.org/2372793002
Cr-Original-Commit-Position: refs/heads/master@{#39891}
Cr-Commit-Position: refs/heads/master@{#39929}