Reworks Channel pausing behavior

Reworks Channel pausing behavior

It turns out creating a Channel paused is not good enough; we actually
need to be able to send some messages, then pause, send more messages,
unpause, send even more messages, and then flush.

This is because of subtleties in how RPHI handles queuing. It queues
messages before the Channel is created, then there is a brief period
between Channel creation and process launch where messages aren't
queued but are sent immediately (but previously queued messages remain
in queue), and then new messages are queued again during process
launch, and finally queueing is turned off after process launch.

This changes Channel to have an explicit Pause() API and gets rid
of the recently added ConnectPaused().

BUG=612500
Committed: https://crrev.com/1018875b737323db9ba00d76705ac70005f019ac
Cr-Commit-Position: refs/heads/master@{#417344}

[Ken Rockot(use gerrit already), 2016-09-07 22:26:40]

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

[commit-bot: I haz the power, 2016-09-07 22:27:08]

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), 2016-09-07 22:44:01]

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

[Ken Rockot(use gerrit already), 2016-09-07 22:44:01]

Apologies for the churn. Some browser tests revealed that I misunderstood RPHI's
queueing behavior and it's even more goofy than I anticipated. This approach
appears to be sufficient, for reals.

[commit-bot: I haz the power, 2016-09-07 23:51:50]

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

[commit-bot: I haz the power, 2016-09-07 23:51:50]

Dry run: This issue passed the CQ dry run.

[jam, 2016-09-08 18:10:01]

lgtm

[Ken Rockot(use gerrit already), 2016-09-08 18:18:12]

The CQ bit was checked by rockot@chromium.org

[commit-bot: I haz the power, 2016-09-08 18:18:45]

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, 2016-09-08 18:25:48]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-09-08 18:30:13]

Description was changed from

==========
Reworks Channel pausing behavior

It turns out creating a Channel paused is not good enough; we actually
need to be able to send some messages, then pause, send more messages,
unpause, send even more messages, and then flush.

This is because of subtleties in how RPHI handles queuing. It queues
messages before the Channel is created, then there is a brief period
between Channel creation and process launch where messages aren't
queued but are sent immediately (but previously queued messages remain
in queue), and then new messages are queued again during process
launch, and finally queueing is turned off after process launch.

This changes Channel to have an explicit Pause() API and gets rid
of the recently added ConnectPaused().

BUG=612500
==========

to

==========
Reworks Channel pausing behavior

It turns out creating a Channel paused is not good enough; we actually
need to be able to send some messages, then pause, send more messages,
unpause, send even more messages, and then flush.

This is because of subtleties in how RPHI handles queuing. It queues
messages before the Channel is created, then there is a brief period
between Channel creation and process launch where messages aren't
queued but are sent immediately (but previously queued messages remain
in queue), and then new messages are queued again during process
launch, and finally queueing is turned off after process launch.

This changes Channel to have an explicit Pause() API and gets rid
of the recently added ConnectPaused().

BUG=612500

Committed: https://crrev.com/1018875b737323db9ba00d76705ac70005f019ac
Cr-Commit-Position: refs/heads/master@{#417344}
==========

[commit-bot: I haz the power, 2016-09-08 18:30:15]

Patchset 1 (id:??) landed as
https://crrev.com/1018875b737323db9ba00d76705ac70005f019ac
Cr-Commit-Position: refs/heads/master@{#417344}