[Extension] Fix build issue on size_t not declared

The error was introduced the patch 88b8aa029d1699 which is to sync
files from crosswalk to t-e-c. The header file <sys/types.h> is
forgot to added in t-e-c.
Also function pointer is wrongly used in the patch 88b8aa029d1699.
Merge pull request #255 from xuzhang/extension_update

[Extension] Fix build issue on size_t not declared