net: Remove typedef net::URLRequestContext URLRequestContext;

BUG=64263
TEST=compiled locally, trybots

Review URL: http://codereview.chromium.org/6338002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@71522 0039d316-1c4b-4281-b951-d872f2087c98
72 files changed