Fix Mac build of r4860
Fix Mac build of r4860

Build error:
test/cctest/test-api.cc: In function 'void ExternalArrayInfoTestHelper(v8::ExternalArrayType)':
test/cctest/test-api.cc:10069: warning: control may reach end of non-void function 'int ExternalArrayElementSize(v8::ExternalArrayType)' being inlined

TBR=ager@chromium.org
Review URL: http://codereview.chromium.org/2826002

git-svn-id: b158db1e4b4ab85d4c9e510fdef4b1e8c614b15b@4861 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh