GitLab

Some cleanup of the file_metadata files (especially for Mac OS).
I moved them under content/browser/download and changed the 
namespace to "content" to match the Linux implementation and the
style guide.

I also included a small change to the Linux-related unittests.

Review URL: https://chromiumcodereview.appspot.com/10821069

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@148910 0039d316-1c4b-4281-b951-d872f2087c98