Fix FFmpeg build for ARM

Add missing config.h.

Review URL: http://codereview.chromium.org/491010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@34315 0039d316-1c4b-4281-b951-d872f2087c98
6 files changed