[vm] Fix flaky crash in StackTraceMallocHookLengthTest.

[vm] Fix flaky crash in StackTraceMallocHookLengthTest.

Remove double initialization of the allocation sample buffer, the second of which triggers the malloc hook.

R=zra@google.com

Committed: https://github.com/dart-lang/sdk/commit/1398ee11af47200c88e3ffb91e1ccc43df0b5976

[rmacnak, 2017-08-09 23:00:04]

rmacnak@google.com changed reviewers:
+ bkonyi@google.com

[zra, 2017-08-10 14:52:37]

zra@google.com changed reviewers:
+ zra@google.com

[zra, 2017-08-10 14:52:38]

lgtm

[rmacnak, 2017-08-10 16:51:58]

Description was changed from

==========
[vm] Fix flaky crash in StackTraceMallocHookLengthTest.

Remove double initialization of the allocation sample buffer, the second of
which runs triggers the malloc hook.
==========

to

==========
[vm] Fix flaky crash in StackTraceMallocHookLengthTest.

Remove double initialization of the allocation sample buffer, the second of
which triggers the malloc hook.
==========

[rmacnak, 2017-08-10 16:52:31]

Description was changed from

==========
[vm] Fix flaky crash in StackTraceMallocHookLengthTest.

Remove double initialization of the allocation sample buffer, the second of
which triggers the malloc hook.
==========

to

==========
[vm] Fix flaky crash in StackTraceMallocHookLengthTest.

Remove double initialization of the allocation sample buffer, the second of
which triggers the malloc hook.

R=zra@google.com

Committed:
https://github.com/dart-lang/sdk/commit/1398ee11af47200c88e3ffb91e1ccc43df0b5976
==========

[rmacnak, 2017-08-10 16:52:32]

Committed patchset #1 (id:1) manually as
1398ee11af47200c88e3ffb91e1ccc43df0b5976 (presubmit successful).