Fix memory leaks in cc/Log_* tests

Fix memory leaks in cc/Log_* tests

Fixes #28347

BUG=
R=vegorov@google.com

Committed: https://github.com/dart-lang/sdk/commit/a47af8ea9e6cc1645b9c34bb25db7c5a2304781d

[Cutch, 2017-01-24 15:57:42]

Description was changed from

==========
Fix memory leaks in cc/Log_* tests

Fixes #28347

BUG=
==========

to

==========
Fix memory leaks in cc/Log_* tests

Fixes #28347

BUG=
==========

[Cutch, 2017-01-24 15:57:43]

johnmccutchan@google.com changed reviewers:
+ vegorov@google.com

[Vyacheslav Egorov (Google), 2017-01-24 16:10:51]

LGTM with a small suggestion.

https://codereview.chromium.org/2651013002/diff/1/runtime/vm/log_test.cc
File runtime/vm/log_test.cc (right):

https://codereview.chromium.org/2651013002/diff/1/runtime/vm/log_test.cc#newc...
runtime/vm/log_test.cc:50: if (test_output_ != NULL) {
No need to check if it is not NULL - free(NULL) is safe.

https://codereview.chromium.org/2651013002/diff/1/runtime/vm/log_test.cc#newc...
runtime/vm/log_test.cc:72: test_output_ = NULL;
Some sort of scoped object might be a better way to manage this. 

TestOutputHelper helper;
TestOutputHelper helper(log);  // if log needs to be deleted too.

something along these lines:

class TOH {
  explicit TOH(Log* log = NULL) : log_(log) { test_output_ = NULL; }
  ~TOH() { free(test_output_); delete log_; }
}

[Cutch, 2017-01-25 21:32:35]

Description was changed from

==========
Fix memory leaks in cc/Log_* tests

Fixes #28347

BUG=
==========

to

==========
Fix memory leaks in cc/Log_* tests

Fixes #28347

BUG=
R=vegorov@google.com

Committed:
https://github.com/dart-lang/sdk/commit/a47af8ea9e6cc1645b9c34bb25db7c5a2304781d
==========

[Cutch, 2017-01-25 21:32:36]

Committed patchset #1 (id:1) manually as
a47af8ea9e6cc1645b9c34bb25db7c5a2304781d (presubmit successful).