Fix HistogramTester::GetAllSamples when empty.

Fix HistogramTester::GetAllSamples when empty.

Fix GetAllSamples to return an empty vector when the histogram has no
samples, instead of crashing.

BUG=

Committed: https://crrev.com/36a9d6f54d27a5a093b8520a4015e8ec1a7c06bd
Cr-Commit-Position: refs/heads/master@{#342634}

[twifkak, 2015-08-06 23:24:09]

twifkak@chromium.org changed reviewers:
+ isherman@chromium.org, phajdan.jr@chromium.org

[Ilya Sherman, 2015-08-07 17:20:12]

LGTM, thanks.

https://codereview.chromium.org/1265403003/diff/1/base/test/histogram_tester.cc
File base/test/histogram_tester.cc (right):

https://codereview.chromium.org/1265403003/diff/1/base/test/histogram_tester....
base/test/histogram_tester.cc:82: if (snapshot) {
optional nit: I'd write this as an early return, personally

[twifkak, 2015-08-07 19:36:38]

https://codereview.chromium.org/1265403003/diff/1/base/test/histogram_tester.cc
File base/test/histogram_tester.cc (right):

https://codereview.chromium.org/1265403003/diff/1/base/test/histogram_tester....
base/test/histogram_tester.cc:82: if (snapshot) {
On 2015/08/07 17:20:12, Ilya Sherman wrote:
> optional nit: I'd write this as an early return, personally

Hmm. Was going to do this, but on second thought, requires duplicating the
return parameter. Kind of a nit-on-a-nit, I know.

[Paweł Hajdan Jr., 2015-08-10 12:59:11]

LGTM

[twifkak, 2015-08-10 15:33:53]

The CQ bit was checked by twifkak@chromium.org

[commit-bot: I haz the power, 2015-08-10 15:34:01]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1265403003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1265403003/1

[commit-bot: I haz the power, 2015-08-10 16:39:38]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-08-10 16:40:36]

Patchset 1 (id:??) landed as
https://crrev.com/36a9d6f54d27a5a093b8520a4015e8ec1a7c06bd
Cr-Commit-Position: refs/heads/master@{#342634}