Use #if DCHECK_IS_ON() in base/strings/string_piece.*

Use #if DCHECK_IS_ON() instead of
(!defined(NDEBUG) || defined(DCHECK_ALWAYS_ON))
in base/strings/string_piece.* because it is
same thing and more succinct and centralized.

Review URL: https://codereview.chromium.org/1328333002

Cr-Commit-Position: refs/heads/master@{#353605}


CrOS-Libchrome-Original-Commit: 570930fc8fdb676b9a60fb4d4a7b029569518da9
2 files changed
tree: abb4744c04cfd1ccc1e79299d130c8eb6978a1d0
  1. base/
  2. build/
  3. components/
  4. dbus/
  5. device/
  6. ipc/
  7. mojo/
  8. testing/
  9. third_party/
  10. ui/