More natural way to serialize GPU tasks and tests.

More natural way to serialize GPU tasks and tests.

This basically takes out the Windows-only hacks and promotes them to
cross-platform behavior driven by --gpu_threading.
    - When --gpu_threading is false (the default), this puts GPU tasks and tests
      together in the same GPU enclave.  They all run serially.
    - When --gpu_threading is true, both the tests and the tasks run totally
      independently, just like the thread-safe CPU-bound work.

BUG=skia:3255
Committed: https://skia.googlesource.com/skia/+/55e88b226ccb85d2c712a9e3e9e1f5bdcaac05ac

[mtklein_C, 2015-01-21 22:12:36]

mtklein@chromium.org changed reviewers:
+ halcanary@google.com

[mtklein, 2015-01-21 22:14:42]

The CQ bit was checked by mtklein@google.com

[commit-bot: I haz the power, 2015-01-21 22:15:45]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/847273005/20001

[commit-bot: I haz the power, 2015-01-21 22:15:46]

Note for Reviewers:
The CQ is waiting for an approval.
If you believe that the CL is not ready yet, or if you would like to L-G-T-M
with comments then please uncheck the CQ checkbox.

Waiting for LGTM from valid reviewer(s) till 2015-01-22 04:15 UTC

[mtklein, 2015-01-21 22:16:15]

The CQ bit was unchecked by mtklein@google.com

[hal.canary, 2015-01-21 22:23:31]

lgtm with a comment

https://codereview.chromium.org/847273005/diff/20001/dm/DM.cpp
File dm/DM.cpp (right):

https://codereview.chromium.org/847273005/diff/20001/dm/DM.cpp#newcode445
dm/DM.cpp:445: break;
What's wrong with

    tg.batch(Task::Run,
             enclaves[kAnyThread_Enclave].begin(),
             enclaves[kAnyThread_Enclave].count());

    tg.add(run_enclave_and_gpu_tests, &enclaves[kGPU_Enclave]);

    tg.add(run_enclave, &enclaves[kPDFSink_Enclave]);

[mtklein, 2015-01-21 23:46:35]

The CQ bit was checked by mtklein@google.com

[commit-bot: I haz the power, 2015-01-21 23:47:26]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/847273005/40001

[commit-bot: I haz the power, 2015-01-21 23:50:16]

Committed patchset #3 (id:40001) as
https://skia.googlesource.com/skia/+/55e88b226ccb85d2c712a9e3e9e1f5bdcaac05ac