Revert 136486 - Delete DownloadRateMonitor since it's never worked right.
(and it complicates other things I want to do)

LayoutTests/media/video-error-does-not-exist.html crashes by r136486.

BUG=73609

Review URL: https://chromiumcodereview.appspot.com/10382109

TBR=fischman@chromium.org

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@136500 0039d316-1c4b-4281-b951-d872f2087c98
6 files changed