Make nacl_helper easily debuggable

chrome/app/nacl_fork_delegate_linux.cc

Index: chrome/app/nacl_fork_delegate_linux.cc
diff --git a/chrome/app/nacl_fork_delegate_linux.cc b/chrome/app/nacl_fork_delegate_linux.cc
index a3723a31745a3b8c0835f4165b7e746f0ce0b570..372a5b75e23112115557433656877c44fe4e01b9 100644
--- a/chrome/app/nacl_fork_delegate_linux.cc
+++ b/chrome/app/nacl_fork_delegate_linux.cc
@@ -26,7 +26,12 @@ NaClForkDelegate::NaClForkDelegate()
       sandboxed_(false),
       fd_(-1) {}
 
+/*
+ * Note these need to match up with their counterparts in nacl_helper_linux.c
+ * and nacl_helper_bootstrap_linux.c.
+ */
 const char kNaClHelperAtZero[] = "--at-zero";
+const char kNaClHelperRDebug[] = "--r_debug=0xXXXXXXXXXXXXXXXX";
 
 void NaClForkDelegate::Init(const bool sandboxed,
                             const int browserdesc,
@@ -59,6 +64,7 @@ void NaClForkDelegate::Init(const bool sandboxed,
     CommandLine cmd_line(helper_bootstrap_exe);
     cmd_line.AppendArgPath(helper_exe);
     cmd_line.AppendArgNative(kNaClHelperAtZero);
+    cmd_line.AppendArgNative(kNaClHelperRDebug);
     base::LaunchOptions options;
     options.fds_to_remap = &fds_to_map;
     options.clone_flags = CLONE_FS | SIGCHLD;