For Linux, create a ZygoteForkDelegate that uses the nacl_helper executable

chrome/nacl.gypi

Index: chrome/nacl.gypi
diff --git a/chrome/nacl.gypi b/chrome/nacl.gypi
index 9b7e6b4f31b8981ddde46bc89dcadc5cef9b42c7..21fbb01efb8592743de1c563ceffe0f9487e8fb8 100644
--- a/chrome/nacl.gypi
+++ b/chrome/nacl.gypi
@@ -28,8 +28,8 @@
           'nacl/nacl_main_platform_delegate_linux.cc',
           'nacl/nacl_main_platform_delegate_mac.mm',
           'nacl/nacl_main_platform_delegate_win.cc',
-          'nacl/nacl_launcher_thread.cc',
-          'nacl/nacl_launcher_thread.h',
+          'nacl/nacl_listener.cc',
+          'nacl/nacl_listener.h',
         ],
         # TODO(gregoryd): consider switching NaCl to use Chrome OS defines
         'conditions': [
@@ -45,6 +45,9 @@
             'defines': [
               '__STDC_LIMIT_MACROS=1',
             ],
+            'sources': [
+              'nacl/nacl_fork_delegate_linux.cc',
+            ],
           },],
         ],
       }],
@@ -141,5 +144,22 @@
         },
       ],
     }],
+    ['OS=="linux"', {
+      'targets': [
+        {
+          'target_name': 'nacl_helper',
+          'type': 'executable',
+          'include_dirs': [
+            '..',
+          ],
+          'dependencies': [
+            'nacl',
+          ],
+          'sources': [
+            '../chrome/nacl/nacl_helper_linux.cc',
+          ],
+        },
+      ],
+    }],
   ],
 }