[Temp] Backport https://codereview.chromium.org/560553007 from upstream
[Temp] Backport https://codereview.chromium.org/560553007 from upstream

Fix compilation with OS X SDK 10.9.

hgl888/chromium-crosswalk-efl,hgl888/chromium-crosswalk-efl,crosswalk-project/chromium-crosswalk-efl,crosswalk-project/chromium-crosswalk-efl,crosswalk-project/chromium-crosswalk-efl,crosswalk-project/chromium-crosswalk-efl,crosswalk-project/chromium-crosswalk-efl,hgl888/chromium-crosswalk-efl,hgl888/chromium-crosswalk-efl,hgl888/chromium-crosswalk-efl,crosswalk-project/chromium-crosswalk-efl,hgl888/chromium-crosswalk-efl,crosswalk-project/chromium-crosswalk-efl,hgl888/chromium-crosswalk-efl,crosswalk-project/chromium-crosswalk-efl,hgl888/chromium-crosswalk-efl,hgl888/chromium-crosswalk-efl,crosswalk-project/chromium-crosswalk-efl,hgl888/chromium-crosswalk-efl