[refactor] Remove WebArrayBuffer from unittests, since now using std::vector.

This is a cleanup following https://codereview.chromium.org/233733004/.

BUG=245025

Review URL: https://codereview.chromium.org/251213006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@267375 0039d316-1c4b-4281-b951-d872f2087c98
5 files changed