Temporarily allow timeout for one mozilla test.

BUG=v8:2018
Review URL: https://chromiumcodereview.appspot.com/9813008

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11106 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

test/mozilla/mozilla.status

@@ -69,6 +69,9 @@ js1_5/Array/regress-465980-02: SKIP
 ecma_3/Date/15.9.3.2-1: SKIP
 js1_2/function/Number: SKIP
 
+# TODO(2018): Temporarily allow timeout in debug mode.
+js1_5/GC/regress-203278-2: PASS || TIMEOUT if $mode == debug
+
 ##################### SLOW TESTS #####################
 
 # This takes a long time to run (~100 seconds). It should only be run