Added regression test for base::JoinString given a null StringPiece.

Added regression test for base::JoinString given a null StringPiece.

This tests against what was previously undefined behaviour (passing a
null pointer to the std::string constructor), introduced in r452432 and
inadvertently fixed in r454189. These tests won't necessarily catch
future undefined behaviour (because the standard library doesn't
actually seem to mind being given a null pointer) but we stand a better
chance of finding it if there are tests.

BUG=698073
Review-Url: https://codereview.chromium.org/2733473002
Cr-Commit-Position: refs/heads/master@{#454817}
Committed: https://chromium.googlesource.com/chromium/src/+/601ab6b021ca49678a407f4feb66a313318c18aa

[Matt Giuca, 2017-03-02 23:50:04]

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

[commit-bot: I haz the power, 2017-03-02 23:50:36]

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

[Matt Giuca, 2017-03-02 23:50:47]

mgiuca@chromium.org changed reviewers:
+ dcheng@chromium.org

[commit-bot: I haz the power, 2017-03-03 00:05:10]

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

[commit-bot: I haz the power, 2017-03-03 00:05:11]

Dry run: This issue passed the CQ dry run.

[dcheng, 2017-03-03 09:11:08]

lgtm

https://codereview.chromium.org/2733473002/diff/1/base/strings/string_util_un...
File base/strings/string_util_unittest.cc (right):

https://codereview.chromium.org/2733473002/diff/1/base/strings/string_util_un...
base/strings/string_util_unittest.cc:808: JoinString({kA, kB, kC,
StringPiece16()}, separator));
This doesn't seem quite equivalent, though I'm OK with it.

[Matt Giuca, 2017-03-06 02:39:57]

https://codereview.chromium.org/2733473002/diff/1/base/strings/string_util_un...
File base/strings/string_util_unittest.cc (right):

https://codereview.chromium.org/2733473002/diff/1/base/strings/string_util_un...
base/strings/string_util_unittest.cc:808: JoinString({kA, kB, kC,
StringPiece16()}, separator));
On 2017/03/03 09:11:08, dcheng wrote:
> This doesn't seem quite equivalent, though I'm OK with it.

It's not equivalent; I deliberately changed it to test the edge case of a null
StringPiece that *isn't* in the first position (since there was a special case
for the first position, and may be again).

(StringPiece() and StringPiece("") are essentially the same, but as we've seen,
StringPiece() has this edge case where data() returns nullptr, so it's more
important to test for that.)

[Matt Giuca, 2017-03-06 02:40:05]

The CQ bit was checked by mgiuca@chromium.org

[commit-bot: I haz the power, 2017-03-06 02:40:25]

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, 2017-03-06 03:05:29]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1488768005154580, "parent_rev":
"9eba8ffcc405012f235a5bfb5ce49485a746b379", "commit_rev":
"601ab6b021ca49678a407f4feb66a313318c18aa"}

[commit-bot: I haz the power, 2017-03-06 03:06:21]

Description was changed from

==========
Added regression test for base::JoinString given a null StringPiece.

This tests against what was previously undefined behaviour (passing a
null pointer to the std::string constructor), introduced in r452432 and
inadvertently fixed in r454189. These tests won't necessarily catch
future undefined behaviour (because the standard library doesn't
actually seem to mind being given a null pointer) but we stand a better
chance of finding it if there are tests.

BUG=698073
==========

to

==========
Added regression test for base::JoinString given a null StringPiece.

This tests against what was previously undefined behaviour (passing a
null pointer to the std::string constructor), introduced in r452432 and
inadvertently fixed in r454189. These tests won't necessarily catch
future undefined behaviour (because the standard library doesn't
actually seem to mind being given a null pointer) but we stand a better
chance of finding it if there are tests.

BUG=698073

Review-Url: https://codereview.chromium.org/2733473002
Cr-Commit-Position: refs/heads/master@{#454817}
Committed:
https://chromium.googlesource.com/chromium/src/+/601ab6b021ca49678a407f4feb66...
==========

[commit-bot: I haz the power, 2017-03-06 03:06:22]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/601ab6b021ca49678a407f4feb66...