Make nacl_helper easily debuggable

chrome/nacl/nacl_helper_bootstrap_linux.x

Index: chrome/nacl/nacl_helper_bootstrap_linux.x
diff --git a/chrome/nacl/nacl_helper_bootstrap_linux.x b/chrome/nacl/nacl_helper_bootstrap_linux.x
index b33a5f64e2cd913bc32a7661c9294ccf7ea28226..3f93a0024403e8b21be832b203b360c4c5a6dd80 100644
--- a/chrome/nacl/nacl_helper_bootstrap_linux.x
+++ b/chrome/nacl/nacl_helper_bootstrap_linux.x
@@ -48,6 +48,7 @@ PHDRS {
   text PT_LOAD FILEHDR PHDRS;
   data PT_LOAD;
   reserve PT_LOAD FLAGS(0);
+  r_debug PT_LOAD;
   note PT_NOTE;
   stack PT_GNU_STACK FLAGS(6);	/* RW, no E */
 }
@@ -112,6 +113,15 @@ SECTIONS {
   } :reserve
 
   /*
+   * This must be placed above the reserved address space, so it won't
+   * be clobbered by NaCl.  We want this to be visible at its fixed address
+   * in the memory image so the debugger can make sense of things.
+   */
+  .r_debug : {
+    *(.r_debug)
+  } :r_debug
+
+  /*
    * These are empty input sections the linker generates.
    * If we don't discard them, they pollute the flags in the output segment.
    */