Mojo: Move waiting APIs to public library

Mojo: Move waiting APIs to public library

This wipes out all blocking wait primitives from the core
API and reimplements them in the public C++ library on
top of the core Watcher API.

This gives us the freedom to more efficiently integrate
with other non-Mojo sync operations in the system.

The new public wait APIs omit any notion of timeout as
it was never used in practice. All waits are indefinite.
(It is still possible to implement timed waiters if/when
needed.)

BUG=700171
Review-Url: https://codereview.chromium.org/2744943002
Cr-Commit-Position: refs/heads/master@{#457856}
Committed: https://chromium.googlesource.com/chromium/src/+/a9d566a1d6b27589589dcfeb81ad7694479df3a5

[Ken Rockot(use gerrit already), 2017-03-11 00:49:09]

The CQ bit was checked by rockot@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-03-11 00:49:30]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[Ken Rockot(use gerrit already), 2017-03-11 00:52:39]

Description was changed from

==========
Mojo: Move waiting APIs to public library

This wipes out all blocking wait primitives from the core
API and reimplements them in the public C++ library on
top of the core Watcher API.

BUG=700171
==========

to

==========
Mojo: Move waiting APIs to public library

This wipes out all blocking wait primitives from the core
API and reimplements them in the public C++ library on
top of the core Watcher API.

This gives us the freedom to more efficiently integrate
with other non-Mojo sync operations in the system.

The new public wait APIs omit any notion of timeout as
it was never used in practice. All waits are indefinite.
(It is still possible to implement timed waiters if/when
needed.)

Wait APIs have also been removed from the Java support
library, as they were unused. waitMany removed from JS.
MojoQueryHandleSignalsState equivalents added for both
languages to satisfy the handful of previous 0-deadline
waits in use there.

BUG=700171
==========

[commit-bot: I haz the power, 2017-03-11 00:54:30]

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

[commit-bot: I haz the power, 2017-03-11 00:54:31]

Dry run: Try jobs failed on following builders:
  chromium_presubmit on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/chromium_presub...)
  ios-device on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios-device/builds...)
  mac_chromium_rel_ng on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_rel_...)

[Ken Rockot(use gerrit already), 2017-03-12 21:50:12]

The CQ bit was checked by rockot@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-03-12 21:50:21]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-03-12 21:54:51]

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

[commit-bot: I haz the power, 2017-03-12 21:54:52]

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

[Ken Rockot(use gerrit already), 2017-03-12 22:22:21]

The CQ bit was checked by rockot@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-03-12 22:22:38]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-03-12 22:26:47]

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

[commit-bot: I haz the power, 2017-03-12 22:26:47]

Dry run: Try jobs failed on following builders:
  linux_chromium_chromeos_rel_ng on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)
  ios-simulator on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios-simulator/bui...)

[Ken Rockot(use gerrit already), 2017-03-13 16:23:32]

The CQ bit was checked by rockot@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-03-13 16:23:58]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-03-13 16:29:35]

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

[commit-bot: I haz the power, 2017-03-13 16:29:36]

Dry run: Try jobs failed on following builders:
  android_n5x_swarming_rel on master.tryserver.chromium.android (JOB_FAILED,
https://build.chromium.org/p/tryserver.chromium.android/builders/android_n5x_...)
  ios-simulator on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios-simulator/bui...)
  ios-simulator-xcode-clang on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios-simulator-xco...)
  mac_chromium_rel_ng on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_rel_...)

[Ken Rockot(use gerrit already), 2017-03-13 16:38:59]

The CQ bit was checked by rockot@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-03-13 16:39:19]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-03-13 16:45:09]

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

[commit-bot: I haz the power, 2017-03-13 16:45:10]

Dry run: Try jobs failed on following builders:
  android_clang_dbg_recipe on master.tryserver.chromium.android (JOB_FAILED,
https://build.chromium.org/p/tryserver.chromium.android/builders/android_clan...)
  linux_android_rel_ng on master.tryserver.chromium.android (JOB_FAILED,
https://build.chromium.org/p/tryserver.chromium.android/builders/linux_androi...)
  chromium_presubmit on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/chromium_presub...)
  linux_chromium_rel_ng on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)
  linux_chromium_tsan_rel_ng on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)
  ios-device on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios-device/builds...)
  ios-device-xcode-clang on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios-device-xcode-...)
  ios-simulator on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios-simulator/bui...)
  mac_chromium_rel_ng on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_rel_...)

[Ken Rockot(use gerrit already), 2017-03-13 17:28:13]

Description was changed from

==========
Mojo: Move waiting APIs to public library

This wipes out all blocking wait primitives from the core
API and reimplements them in the public C++ library on
top of the core Watcher API.

This gives us the freedom to more efficiently integrate
with other non-Mojo sync operations in the system.

The new public wait APIs omit any notion of timeout as
it was never used in practice. All waits are indefinite.
(It is still possible to implement timed waiters if/when
needed.)

Wait APIs have also been removed from the Java support
library, as they were unused. waitMany removed from JS.
MojoQueryHandleSignalsState equivalents added for both
languages to satisfy the handful of previous 0-deadline
waits in use there.

BUG=700171
==========

to

==========
Mojo: Move waiting APIs to public library

This wipes out all blocking wait primitives from the core
API and reimplements them in the public C++ library on
top of the core Watcher API.

This gives us the freedom to more efficiently integrate
with other non-Mojo sync operations in the system.

The new public wait APIs omit any notion of timeout as
it was never used in practice. All waits are indefinite.
(It is still possible to implement timed waiters if/when
needed.)

BUG=700171
==========

[Ken Rockot(use gerrit already), 2017-03-15 23:31:55]

The CQ bit was checked by rockot@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-03-15 23:33:27]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[Ken Rockot(use gerrit already), 2017-03-15 23:34:19]

rockot@chromium.org changed reviewers:
+ yzshen@chromium.org

[Ken Rockot(use gerrit already), 2017-03-15 23:34:20]

Last big one, though the size is deceptive. Mostly deletion and mechanical call
site updates.

Interesting changes are in mojo/public/cpp/system and
mojo/public/cpp/bindings/lib. Tiny bit of non-trivial stuff in EDK where
Awakables are surgically removed from dispatchers.

PTAL. Thanks!

[commit-bot: I haz the power, 2017-03-15 23:39:30]

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

[commit-bot: I haz the power, 2017-03-15 23:39:32]

Dry run: Try jobs failed on following builders:
  android_arm64_dbg_recipe on master.tryserver.chromium.android (JOB_FAILED,
https://build.chromium.org/p/tryserver.chromium.android/builders/android_arm6...)
  cast_shell_linux on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/cast_shell_linu...)
  linux_chromium_rel_ng on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)
  ios-device-xcode-clang on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios-device-xcode-...)
  ios-simulator on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios-simulator/bui...)
  ios-simulator-xcode-clang on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios-simulator-xco...)
  mac_chromium_compile_dbg_ng on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_comp...)

[Ken Rockot(use gerrit already), 2017-03-16 02:31:52]

The CQ bit was checked by rockot@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-03-16 02:32:09]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-03-16 02:46:59]

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

[commit-bot: I haz the power, 2017-03-16 02:47:01]

Dry run: Try jobs failed on following builders:
  cast_shell_linux on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/cast_shell_linu...)
  mac_chromium_rel_ng on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_rel_...)

[Ken Rockot(use gerrit already), 2017-03-16 03:55:39]

The CQ bit was checked by rockot@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-03-16 03:55:52]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-03-16 04:09:59]

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

[commit-bot: I haz the power, 2017-03-16 04:10:00]

Dry run: Try jobs failed on following builders:
  cast_shell_linux on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/cast_shell_linu...)
  mac_chromium_rel_ng on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_rel_...)

[Ken Rockot(use gerrit already), 2017-03-16 04:16:20]

The CQ bit was checked by rockot@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-03-16 04:16:45]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-03-16 04:20:46]

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

[commit-bot: I haz the power, 2017-03-16 04:20:47]

Dry run: Try jobs failed on following builders:
  chromium_presubmit on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/chromium_presub...)
  ios-device on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios-device/builds...)
  ios-device-xcode-clang on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios-device-xcode-...)
  ios-simulator on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios-simulator/bui...)
  ios-simulator-xcode-clang on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios-simulator-xco...)

[Ken Rockot(use gerrit already), 2017-03-16 13:17:42]

The CQ bit was checked by rockot@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-03-16 13:17:55]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-03-16 13:53:37]

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

[commit-bot: I haz the power, 2017-03-16 13:53:38]

Dry run: Try jobs failed on following builders:
  win_chromium_x64_rel_ng on master.tryserver.chromium.win (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.win/builders/win_chromium_x64_...)
  win_clang on master.tryserver.chromium.win (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.win/builders/win_clang/builds/...)

[Ken Rockot(use gerrit already), 2017-03-16 18:29:37]

The CQ bit was checked by rockot@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-03-16 18:30:21]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-03-16 19:12:46]

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

[commit-bot: I haz the power, 2017-03-16 19:12:47]

Dry run: Try jobs failed on following builders:
  win_clang on master.tryserver.chromium.win (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.win/builders/win_clang/builds/...)

[Ken Rockot(use gerrit already), 2017-03-16 19:23:17]

The CQ bit was checked by rockot@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-03-16 19:23:47]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-03-16 19:59:33]

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

[commit-bot: I haz the power, 2017-03-16 19:59:35]

Dry run: Try jobs failed on following builders:
  ios-simulator on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios-simulator/bui...)
  win_chromium_compile_dbg_ng on master.tryserver.chromium.win (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.win/builders/win_chromium_comp...)

[Ken Rockot(use gerrit already), 2017-03-16 20:11:08]

The CQ bit was checked by rockot@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-03-16 20:12:05]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-03-16 21:16:48]

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

[commit-bot: I haz the power, 2017-03-16 21:16:49]

Dry run: Try jobs failed on following builders:
  win_chromium_x64_rel_ng on master.tryserver.chromium.win (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.win/builders/win_chromium_x64_...)

[Ken Rockot(use gerrit already), 2017-03-16 21:23:18]

The CQ bit was checked by rockot@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-03-16 21:23:55]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-03-16 22:31:10]

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

[commit-bot: I haz the power, 2017-03-16 22:31:11]

Dry run: Try jobs failed on following builders:
  ios-simulator on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios-simulator/bui...)

[Ken Rockot(use gerrit already), 2017-03-17 16:35:20]

The CQ bit was checked by rockot@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-03-17 16:35:41]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[yzshen1, 2017-03-17 17:10:28]

LGTM with a few nits.

Thanks!

https://codereview.chromium.org/2744943002/diff/250001/mojo/public/c/system/t...
File mojo/public/c/system/types.h (right):

https://codereview.chromium.org/2744943002/diff/250001/mojo/public/c/system/t...
mojo/public/c/system/types.h:148: //       watching for this
|MOJO_RESULT_FAILED_PRECONDITION|.
nit: is it "watching for this *with* ..."?

https://codereview.chromium.org/2744943002/diff/250001/mojo/public/cpp/bindin...
File mojo/public/cpp/bindings/lib/connector.cc (right):

https://codereview.chromium.org/2744943002/diff/250001/mojo/public/cpp/bindin...
mojo/public/cpp/bindings/lib/connector.cc:88: } else if (deadline ==
MOJO_DEADLINE_INDEFINITE) {
nit: no need to use "else" here.

https://codereview.chromium.org/2744943002/diff/250001/mojo/public/cpp/system...
File mojo/public/cpp/system/wait.h (right):

https://codereview.chromium.org/2744943002/diff/250001/mojo/public/cpp/system...
mojo/public/cpp/system/wait.h:38: // the corresponding signals in |signals|
become satisfied or to have all of the
nit: At the first glance, I thought this method aborts only when all handles
become unsatisfiable.

I feel that the original comment for MojoWaitMany seems a little more clear:
// Waits on |handles[0]|, ..., |handles[num_handles-1]| until:	
//   - (At least) one handle satisfies a signal indicated in its respective	
//     |signals[0]|, ..., |signals[num_handles-1]|.	
//   - It becomes known that no signal in some |signals[i]| will ever be	
//     satisfied.
// This means that |MojoWaitMany()| behaves as if |MojoWait()| were called on	
// each handle/signals pair simultaneously, completing when the first	
// |MojoWait()| would complete.
...

WDYT? Thanks!

https://codereview.chromium.org/2744943002/diff/250001/mojo/public/cpp/system...
mojo/public/cpp/system/wait.h:59: //       or if any of |handles|, |signals|, or
|result_index| is null.
I thought |result_index| is allowed to be null?

https://codereview.chromium.org/2744943002/diff/250001/services/tracing/servi...
File services/tracing/service.cc (right):

https://codereview.chromium.org/2744943002/diff/250001/services/tracing/servi...
services/tracing/service.cc:119: mojo::WaitMany(handles.data(), signals.data(),
handles.size(),
[just to double check] At first glance this seems a legitimate use case of
deadline?

[Ken Rockot(use gerrit already), 2017-03-17 17:55:59]

The CQ bit was checked by rockot@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-03-17 17:56:28]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[Ken Rockot(use gerrit already), 2017-03-17 17:58:52]

Thank you!

https://codereview.chromium.org/2744943002/diff/250001/mojo/public/c/system/t...
File mojo/public/c/system/types.h (right):

https://codereview.chromium.org/2744943002/diff/250001/mojo/public/c/system/t...
mojo/public/c/system/types.h:148: //       watching for this
|MOJO_RESULT_FAILED_PRECONDITION|.
On 2017/03/17 at 17:10:27, yzshen1 wrote:
> nit: is it "watching for this *with* ..."?

Done

https://codereview.chromium.org/2744943002/diff/250001/mojo/public/cpp/bindin...
File mojo/public/cpp/bindings/lib/connector.cc (right):

https://codereview.chromium.org/2744943002/diff/250001/mojo/public/cpp/bindin...
mojo/public/cpp/bindings/lib/connector.cc:88: } else if (deadline ==
MOJO_DEADLINE_INDEFINITE) {
On 2017/03/17 at 17:10:27, yzshen1 wrote:
> nit: no need to use "else" here.

Done

https://codereview.chromium.org/2744943002/diff/250001/mojo/public/cpp/system...
File mojo/public/cpp/system/wait.h (right):

https://codereview.chromium.org/2744943002/diff/250001/mojo/public/cpp/system...
mojo/public/cpp/system/wait.h:38: // the corresponding signals in |signals|
become satisfied or to have all of the
On 2017/03/17 at 17:10:27, yzshen1 wrote:
> nit: At the first glance, I thought this method aborts only when all handles
become unsatisfiable.
> 
> I feel that the original comment for MojoWaitMany seems a little more clear:
> // Waits on |handles[0]|, ..., |handles[num_handles-1]| until:	
> //   - (At least) one handle satisfies a signal indicated in its respective	
> //     |signals[0]|, ..., |signals[num_handles-1]|.	
> //   - It becomes known that no signal in some |signals[i]| will ever be	
> //     satisfied.
> // This means that |MojoWaitMany()| behaves as if |MojoWait()| were called on	
> // each handle/signals pair simultaneously, completing when the first	
> // |MojoWait()| would complete.
> ...
> 
> WDYT? Thanks!

Agreed. Fixed!

https://codereview.chromium.org/2744943002/diff/250001/mojo/public/cpp/system...
mojo/public/cpp/system/wait.h:59: //       or if any of |handles|, |signals|, or
|result_index| is null.
On 2017/03/17 at 17:10:27, yzshen1 wrote:
> I thought |result_index| is allowed to be null?

Indeed. Outdated comment. :)

Fixed!

https://codereview.chromium.org/2744943002/diff/250001/services/tracing/servi...
File services/tracing/service.cc (right):

https://codereview.chromium.org/2744943002/diff/250001/services/tracing/servi...
services/tracing/service.cc:119: mojo::WaitMany(handles.data(), signals.data(),
handles.size(),
On 2017/03/17 at 17:10:27, yzshen1 wrote:
> [just to double check] At first glance this seems a legitimate use case of
deadline?

Yep. I've added a TODO to fix it. It shouldn't be a problem for now since a) not
used in production and b) only an issue if a trace collector is misbehaving or
unresponsive.

[Ken Rockot(use gerrit already), 2017-03-17 17:59:02]

The CQ bit was unchecked by rockot@chromium.org

[Ken Rockot(use gerrit already), 2017-03-17 17:59:03]

The CQ bit was checked by rockot@chromium.org

[Ken Rockot(use gerrit already), 2017-03-17 17:59:04]

The patchset sent to the CQ was uploaded after l-g-t-m from yzshen@chromium.org
Link to the patchset: https://codereview.chromium.org/2744943002/#ps290001
(title: ".")

[commit-bot: I haz the power, 2017-03-17 17:59:21]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-03-17 19:36:21]

CQ is committing da patch.

Bot data: {"patchset_id": 290001, "attempt_start_ts": 1489773543817150,
"parent_rev": "b4325a20870946edaecbe18d2ab0e2e9c01911aa", "commit_rev":
"cef40fa97eaf6288e94394f59b20a5412d43ea9d"}

[commit-bot: I haz the power, 2017-03-17 19:41:00]

CQ is committing da patch.

Bot data: {"patchset_id": 290001, "attempt_start_ts": 1489773543817150,
"parent_rev": "0bd34dbe7b000fc958fdf0adc4b12ea5c5ccea44", "commit_rev":
"a9d566a1d6b27589589dcfeb81ad7694479df3a5"}

[commit-bot: I haz the power, 2017-03-17 19:41:44]

Description was changed from

==========
Mojo: Move waiting APIs to public library

This wipes out all blocking wait primitives from the core
API and reimplements them in the public C++ library on
top of the core Watcher API.

This gives us the freedom to more efficiently integrate
with other non-Mojo sync operations in the system.

The new public wait APIs omit any notion of timeout as
it was never used in practice. All waits are indefinite.
(It is still possible to implement timed waiters if/when
needed.)

BUG=700171
==========

to

==========
Mojo: Move waiting APIs to public library

This wipes out all blocking wait primitives from the core
API and reimplements them in the public C++ library on
top of the core Watcher API.

This gives us the freedom to more efficiently integrate
with other non-Mojo sync operations in the system.

The new public wait APIs omit any notion of timeout as
it was never used in practice. All waits are indefinite.
(It is still possible to implement timed waiters if/when
needed.)

BUG=700171

Review-Url: https://codereview.chromium.org/2744943002
Cr-Commit-Position: refs/heads/master@{#457856}
Committed:
https://chromium.googlesource.com/chromium/src/+/a9d566a1d6b27589589dcfeb81ad...
==========

[commit-bot: I haz the power, 2017-03-17 19:41:46]

Committed patchset #16 (id:290001) as
https://chromium.googlesource.com/chromium/src/+/a9d566a1d6b27589589dcfeb81ad...