Revert 228002 "Enable cast_unittests"

Breaks compile on the `All` target on win_x64_rel. Note that this is only
built by default on manually submitted tryjobs. Not CQ or waterfall.
(see bug). For the errors see, e.g.,
http://build.chromium.org/p/tryserver.chromium/builders/win_x64_rel/builds/45000/

BUG=304877

> Enable cast_unittests
> And fixed associated errors
> 
> Review URL: https://codereview.chromium.org/26486005

TBR=pwestin@google.com

Review URL: https://codereview.chromium.org/27141002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@228412 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 228412