PNaCl sandboxed linker: Use new IRT interface instead of using SRPC directly

BUG=https://code.google.com/p/chromium/issues/detail?id=302078
TEST=NaCl's Scons-based sandboxed linker tests
R=jvoung@chromium.org

Review URL: https://codereview.chromium.org/904583002
2 files changed