Fix http/tests/cache random-order flakiness

Fix http/tests/cache random-order flakiness

post-image-to-verify.php touches a file to check if it has been loaded, but
multiple tests use the file. This change fixes the issue by separating the
temporary file.

BUG=663865
Committed: https://crrev.com/9f7c2d8eddada5b0fe0b123312b4e041b67c3879
Cr-Commit-Position: refs/heads/master@{#435144}

[yhirano, 2016-11-29 09:54:41]

The CQ bit was checked by yhirano@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-11-29 09:55:11]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[yhirano, 2016-11-29 09:56:14]

yhirano@chromium.org changed reviewers:
+ hiroshige@chromium.org

[commit-bot: I haz the power, 2016-11-29 10:47:39]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-11-29 10:47:40]

Dry run: This issue passed the CQ dry run.

[hiroshige, 2016-11-30 07:41:20]

lgtm.

Just memo: I thought adding comments saying "Modify filename when you
copy-and-paste" might be helpful for preventing the same issue in the future,
but I'm not sure how it is useful because similar issues of using the same URL
across multiple tests are more prevailing in layout tests.

[yhirano, 2016-11-30 07:45:34]

The CQ bit was checked by yhirano@chromium.org

[commit-bot: I haz the power, 2016-11-30 07:46:13]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-11-30 07:54:22]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1480491934122130, "parent_rev":
"d7e14971361af51e56489b940e7dcacb8c4e432c", "commit_rev":
"578cec13215ac29718388bc25efd4d50e669851b"}

[commit-bot: I haz the power, 2016-11-30 07:54:47]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-11-30 07:56:23]

Description was changed from

==========
Fix http/tests/cache random-order flakiness

post-image-to-verify.php touches a file to check if it has been loaded, but
multiple tests use the file. This change fixes the issue by separating the
temporary file.

BUG=663865
==========

to

==========
Fix http/tests/cache random-order flakiness

post-image-to-verify.php touches a file to check if it has been loaded, but
multiple tests use the file. This change fixes the issue by separating the
temporary file.

BUG=663865

Committed: https://crrev.com/9f7c2d8eddada5b0fe0b123312b4e041b67c3879
Cr-Commit-Position: refs/heads/master@{#435144}
==========

[commit-bot: I haz the power, 2016-11-30 07:56:24]

Patchset 1 (id:??) landed as
https://crrev.com/9f7c2d8eddada5b0fe0b123312b4e041b67c3879
Cr-Commit-Position: refs/heads/master@{#435144}