Remove weak references from IRT startup code as well.
Remove weak references from IRT startup code as well.

This fixes an omission in earlier CL: http://codereview.chromium.org/8479004

This should fix the ppapi_simple_* tests on the PNaCl bots which went red at r7111.

TBR=Roland McGrath, jvoung

BUG= http://code.google.com/p/nativeclient/issues/detail?id=1096
Review URL: http://codereview.chromium.org/8498002

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@7118 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

sbc100/native_client,sbc100/native_client,nacl-webkit/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,nacl-webkit/native_client,nacl-webkit/native_client,nacl-webkit/native_client,sbc100/native_client,nacl-webkit/native_client