When launching PNaCl helper nexes, explicitly disable IRT loading.

This is done by setting the irt_fd to -1.  However NaCl
currently errors out when given -1, so this depends on a
NaCl-side sel_ldr change which will understand that -1 means
skip loading: https://codereview.chromium.org/11743028/

BUG= http://code.google.com/p/nativeclient/issues/detail?id=3241
TEST= manual (patch in NaCl side CL and run PNaCl w/ TOOLS_REVISION at 10509).

Review URL: https://codereview.chromium.org/11761025

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@176389 0039d316-1c4b-4281-b951-d872f2087c98
18 files changed