Switch to fetching NPAPI requests through the browser process instead of going through the renderer.

BUG=286074
R=ananta@chromium.org

Review URL: https://codereview.chromium.org/25087005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@226031 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 226031