nacl sources should be included conditionally

chrome/chrome_renderer.gypi

Index: chrome/chrome_renderer.gypi
diff --git a/chrome/chrome_renderer.gypi b/chrome/chrome_renderer.gypi
index 67df6171185cda18ee68f5ac144ddab3b91b54a1..7ee6367464e8461b5eb25841be0b450ce2cec9cf 100755
--- a/chrome/chrome_renderer.gypi
+++ b/chrome/chrome_renderer.gypi
@@ -102,7 +102,6 @@
         'renderer/gpu_channel_host.h',
         'renderer/localized_error.cc',
         'renderer/localized_error.h',
-        'renderer/nacl_desc_wrapper_chrome.cc',
         'renderer/navigation_state.h',
         'renderer/notification_provider.cc',
         'renderer/notification_provider.h',
@@ -184,6 +183,9 @@
           'dependencies': [
             'nacl',
           ],
+          'sources': [
+            'renderer/nacl_desc_wrapper_chrome.cc',
+          ],
         }],
         # Linux-specific rules.
         ['OS=="linux"', {