[Telemetry] Test for display tracing

[Telemetry] Test for display tracing

BUG=535731
Committed: https://crrev.com/b076edb74bbc896950af6e50c374c528ec0b4235
Cr-Commit-Position: refs/heads/master@{#351099}

[Zhen Wang, 2015-09-24 23:47:08]

zhenw@chromium.org changed reviewers:
+ nednguyen@google.com

[Zhen Wang, 2015-09-24 23:47:09]

ptal

[nednguyen, 2015-09-26 00:14:06]

From the high level point of view, I think what we want to assert is after
calling Stop(), the next call of StartTracing will always succeed, no matter
what.

Testing the internal state of _surface_stats_collector isn't the good kind of
API testing. i.e: if people change the implementation of StartDisplayTracing to
not check using _surface_stats_collector, our test will lose it usefulness.

https://codereview.chromium.org/1366133002/diff/1/tools/telemetry/telemetry/i...
File
tools/telemetry/telemetry/internal/platform/tracing_agent/display_tracing_agent_unittest.py
(right):

https://codereview.chromium.org/1366133002/diff/1/tools/telemetry/telemetry/i...
tools/telemetry/telemetry/internal/platform/tracing_agent/display_tracing_agent_unittest.py:14:
android_platform_backend.AndroidPlatformBackend):
Nit: This should live in tools/telemetry/telemetry/testing/fakes/__init__.py

[Zhen Wang, 2015-09-28 15:40:58]

updated the tests.

https://codereview.chromium.org/1366133002/diff/1/tools/telemetry/telemetry/i...
File
tools/telemetry/telemetry/internal/platform/tracing_agent/display_tracing_agent_unittest.py
(right):

https://codereview.chromium.org/1366133002/diff/1/tools/telemetry/telemetry/i...
tools/telemetry/telemetry/internal/platform/tracing_agent/display_tracing_agent_unittest.py:14:
android_platform_backend.AndroidPlatformBackend):
On 2015/09/26 00:14:06, nednguyen wrote:
> Nit: This should live in tools/telemetry/telemetry/testing/fakes/__init__.py

I think this still belongs here because it is tailored for display tracing. And
we need it to subclass the real android platform backend to control the stop
tracing behavior. It is not for public API.

[nednguyen, 2015-09-28 16:41:28]

lgtm

[Zhen Wang, 2015-09-28 16:42:59]

The CQ bit was checked by zhenw@chromium.org

[commit-bot: I haz the power, 2015-09-28 16:43:41]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1366133002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1366133002/20001

[commit-bot: I haz the power, 2015-09-28 19:19:03]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-09-28 19:19:49]

Patchset 2 (id:??) landed as
https://crrev.com/b076edb74bbc896950af6e50c374c528ec0b4235
Cr-Commit-Position: refs/heads/master@{#351099}