Adding stages for request headers and 3rd party attributes

I forgot to do this in CLs http://codereview.chromium.org/10982044/ and
http://codereview.chromium.org/11038031/.

BUG=112155, 143662, 135606
TEST=N/A (docs changes only)
TBR=cduvall@chromium.org

Review URL: https://chromiumcodereview.appspot.com/11185056

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@162770 0039d316-1c4b-4281-b951-d872f2087c98
1 file changed