trace_controller: Makes StopTracing callback ignore empty event strings

trace_controller: Makes StopTracing callback ignore empty event strings

This will give us the flexibility within PowerTracingAgent to signify
that an error occurred (such as bad data coming over the serial
connection).

Committed: https://crrev.com/c214961ef438fcd571f37ff39296feb8df075c65
Cr-Commit-Position: refs/heads/master@{#371587}

[charliea (OOO until 10-5), 2016-01-26 17:56:53]

Patchset #1 (id:1) has been deleted

[charliea (OOO until 10-5), 2016-01-26 17:58:56]

charliea@chromium.org changed reviewers:
+ oysteine@chromium.org

[charliea (OOO until 10-5), 2016-01-26 17:58:57]

https://codereview.chromium.org/1637933002/diff/20001/base/trace_event/tracin...
File base/trace_event/tracing_agent.h (right):

https://codereview.chromium.org/1637933002/diff/20001/base/trace_event/tracin...
base/trace_event/tracing_agent.h:30: // available for the specified agent.
Here I chose to treat both null and empty events_str_ptrs as no trace data. It
felt strange to me otherwise to write out nothing for one and a full trace event
with an empty string in the payload for the other, when in reality both of them
mean "no data available".

[oystein (OOO til 10th of July), 2016-01-26 18:25:40]

lgtm

[charliea (OOO until 10-5), 2016-01-26 18:35:02]

The CQ bit was checked by charliea@chromium.org

[commit-bot: I haz the power, 2016-01-26 18:37:30]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1637933002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1637933002/20001

[commit-bot: I haz the power, 2016-01-26 18:49:35]

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

[commit-bot: I haz the power, 2016-01-26 18:49:36]

Try jobs failed on following builders:
  cast_shell_linux on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/cast_shell_linu...)
  chromeos_daisy_chromium_compile_only_ng on tryserver.chromium.linux
(JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/chromeos_daisy_...)

[charliea (OOO until 10-5), 2016-01-26 19:09:29]

The CQ bit was checked by charliea@chromium.org

[charliea (OOO until 10-5), 2016-01-26 19:09:29]

The patchset sent to the CQ was uploaded after l-g-t-m from
oysteine@chromium.org
Link to the patchset: https://codereview.chromium.org/1637933002/#ps40001
(title: " ")

[commit-bot: I haz the power, 2016-01-26 19:10:08]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1637933002/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1637933002/40001

[commit-bot: I haz the power, 2016-01-26 20:40:21]

Committed patchset #2 (id:40001)

[commit-bot: I haz the power, 2016-01-26 20:41:43]

Description was changed from

==========
trace_controller: Makes StopTracing callback ignore empty event strings

This will give us the flexibility within PowerTracingAgent to signify
that an error occurred (such as bad data coming over the serial
connection).
==========

to

==========
trace_controller: Makes StopTracing callback ignore empty event strings

This will give us the flexibility within PowerTracingAgent to signify
that an error occurred (such as bad data coming over the serial
connection).

Committed: https://crrev.com/c214961ef438fcd571f37ff39296feb8df075c65
Cr-Commit-Position: refs/heads/master@{#371587}
==========

[commit-bot: I haz the power, 2016-01-26 20:41:44]

Patchset 2 (id:??) landed as
https://crrev.com/c214961ef438fcd571f37ff39296feb8df075c65
Cr-Commit-Position: refs/heads/master@{#371587}