Revert 161116 "Remove V8 dependency from blink_platform"

> Remove V8 dependency from blink_platform
> 
> Review URL: https://codereview.chromium.org/54893003

TBR=adamk@chromium.org

Review URL: https://codereview.chromium.org/46163006

git-svn-id: svn://svn.chromium.org/blink/trunk@161117 bbb929c8-8fbe-4397-9dbb-9b2b20218538