Pepper: Delete FileDownloader in trusted plugin.

This simplifies PnaclCoordinator considerably and reduces the total
amount of code in the trusted plugin.

BUG=239656

Review URL: https://codereview.chromium.org/393693004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@284684 0039d316-1c4b-4281-b951-d872f2087c98
15 files changed