Add a switch for using PNaCl Subzero and use it for -O0 translation.

components/nacl/renderer/plugin/pnacl_coordinator.h

Index: components/nacl/renderer/plugin/pnacl_coordinator.h
diff --git a/components/nacl/renderer/plugin/pnacl_coordinator.h b/components/nacl/renderer/plugin/pnacl_coordinator.h
index 1585b5fd5df77c233c39680667484dd61abaabb5..73744903d85badb22518dd1771b2912ef4caa762 100644
--- a/components/nacl/renderer/plugin/pnacl_coordinator.h
+++ b/components/nacl/renderer/plugin/pnacl_coordinator.h
@@ -161,8 +161,10 @@ class PnaclCoordinator {
   // Object file, produced by the translator and consumed by the linker.
   std::vector<TempFile*> obj_files_;
   nacl::scoped_ptr<nacl::DescWrapper> invalid_desc_wrapper_;
-  // Number of split modules (threads) for llc
+  // Number of split modules for llc.
   int split_module_count_;
+  // Number of threads for llc / subzero.
+  int num_threads_;
 
   // Translated nexe file, produced by the linker.
   nacl::scoped_ptr<TempFile> temp_nexe_file_;