Make XmlUnitTestResultPrinter handle failing to open output

This was causing occasional crashes on Fuchsia. See
https://bugs.chromium.org/p/chromium/issues/detail?id=736783#c6 for a
detailed explanation of the conditions under which this can happen.

Bug: 736783, 706592
Change-Id: I5000509d846dd9b8f10b9ae7a58bbfbdd642cc96
Reviewed-on: https://chromium-review.googlesource.com/550200
Reviewed-by: Paweł Hajdan Jr. <phajdan.jr@chromium.org>
Commit-Queue: Scott Graham <scottmg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#482709}

CrOS-Libchrome-Original-Commit: 66411becd2b5a570b5629b64422a17a3583b2d0e
2 files changed
tree: b6bdc52b1258bad937d1f1fcbf8d2a37dc84ed05
  1. base/
  2. build/
  3. components/
  4. dbus/
  5. device/
  6. ipc/
  7. mojo/
  8. testing/
  9. third_party/
  10. ui/