Changed a static cast from static_cast<int> to static_cast<size_t>
that previously introduced a signed/unsigned comparison issue in the
main allocator for V8 (MemoryAllocator::AllocateRawMemory) that could
be used to bypass the V8 allocation limitations or trigger integer
overflows.

Review URL: http://codereview.chromium.org/3027006/show

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@5094 ce2b1a6d-e550-0410-aec6-3dcde31c8c00