This is because since r201066 JSC also uses the preferred language from the system locale instead of falling back to "en" and those tests expect the locale to be en_US. run-javascriptcore-tests does $ENV{LANG}="en_US.UTF-8"; but we are not actually honoring the environment variables at all when using jsc binary. We are using setlocale with a nullptr locale to get the current one, but the current one is always "C", because to set the locale according to the environment variables we need to call setlocale with an empty string as locale. That's done by gtk_init(), which is called by all our binaries (web process, network process, etc.), but not by jsc (because jsc doesn't depend on GTK+). The reason why it has always worked for EFL is because they call ecore_init() in jsc that calls setlocale.
Created attachment 279759 [details] Patch for landing
r201066 made the following tests fail on JSCOnly ARM bots: mozilla-tests.yaml/ecma_3/Date/15.9.5.6.js.mozilla mozilla-tests.yaml/ecma_3/Date/15.9.5.6.js.mozilla-baseline mozilla-tests.yaml/ecma_3/Date/15.9.5.6.js.mozilla-dfg-eager-no-cjit-validate-phases mozilla-tests.yaml/ecma_3/Date/15.9.5.6.js.mozilla-llint but fixed these tests: jsc-layout-tests.yaml/js/script-tests/number-toLocaleString.js.layout jsc-layout-tests.yaml/js/script-tests/number-toLocaleString.js.layout-dfg-eager-no-cjit jsc-layout-tests.yaml/js/script-tests/number-toLocaleString.js.layout-no-cjit jsc-layout-tests.yaml/js/script-tests/number-toLocaleString.js.layout-no-llint
Committed r201383: <http://trac.webkit.org/changeset/201383>