Add a preference to force enable the NaCl plugin as we transition to

chrome/common/pref_names.cc

Index: chrome/common/pref_names.cc
===================================================================
--- chrome/common/pref_names.cc	(revision 97988)
+++ chrome/common/pref_names.cc	(working copy)
@@ -587,6 +587,10 @@
 // enable it by default, we'll want to do so only once.
 const char kPluginsEnabledInternalPDF[] = "plugins.enabled_internal_pdf3";
 
+// When first shipped, the nacl plugin will be disabled by default.  When we
+// enable it by default, we'll want to do so only once.
+const char kPluginsEnabledNaCl[] = "plugins.enabled_nacl";
+
 const char kPluginsShowSetReaderDefaultInfobar[] =
     "plugins.show_set_reader_default";