Convert ARRAYSIZE_UNSAFE -> arraysize in base/.

R=thestig@chromium.org
BUG=423134

Review URL: https://codereview.chromium.org/656033009

Cr-Commit-Position: refs/heads/master@{#299835}
DWORD GetNextChunkSize(size_t current_pos, size_t max_size) {
  return static_cast<DWORD>(((max_size - current_pos) <= UINT_MAX) ?
      (max_size - current_pos) : UINT_MAX);
}

DWORD GetNextChunkSize(size_t current_pos, size_t max_size) {
  return static_cast<DWORD>(((max_size - current_pos) <= UINT_MAX) ?
      (max_size - current_pos) : UINT_MAX);
}
