fix android build by adding build_config.h

BUG=none
TBR=dewittj@chromium.org

Review URL: https://codereview.chromium.org/75663003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@235842 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 235842