Remove default from switch.

BUG=
TEST=

Review URL: https://chromiumcodereview.appspot.com/10555026

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11849 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/hydrogen.cc

@@ -937,10 +937,9 @@ class PostorderProcessor : public ZoneObject {
         }
       case NONE:
         return father_;
-      default:
-        UNREACHABLE();
-        return NULL;
     }
+    UNREACHABLE();
+    return NULL;
   }
 
   // Walks up the stack.