Crash fix: HTTPS server responds with 407 through non-authenticating proxy.

      Now, HttpNetworkTransaction::HandleAuthChallenge returns ERR_INVALID_PROXY_AUTHENTICATE when this is detected.

BUG=61701
TEST=net_unittests --gtest_filter=&quot*HttpsServerRequestsProxyAuthThroughProxy*&quot

Review URL: http://codereview.chromium.org/4575001

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@65225 0039d316-1c4b-4281-b951-d872f2087c98