Fix integer overflow in Windows shared memory handling.

BUG=164490
Review URL: https://codereview.chromium.org/11450016

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@171369 0039d316-1c4b-4281-b951-d872f2087c98
bool SharedMemory::Delete(const std::string& name) {
  return true;
}

bool SharedMemory::Delete(const std::string& name) {
  return true;
}
