Remove the remaining PLATFORM(CHROMIUM) guard in JavaScriptCore
https://bugs.webkit.org/show_bug.cgi?id=114082

Reviewed by Ryosuke Niwa.

* runtime/JSExportMacros.h: Remove the remaining PLATFORM(CHROMIUM) guard.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@147852 268f45cc-cd09-0410-ab3c-d52691b4dbfc