Allow null begin frame sources in cc::Scheduler

Allow null begin frame sources in cc::Scheduler

This adds support to make it possible to set the begin frame source in
Scheduler back to null before setting it to something else again.

This is primarily to support the use case of losing an output surface
(which will provide the begin frame source) before asynchronously later
initializing another output surface (with potentially another source).
In this case, there will be some period of time where there is no valid
begin frame source.  The scheduler owner could provide a fake one, but
I think that's more confusing than helpful.

Depends on https://codereview.chromium.org/1774323003
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Committed: https://crrev.com/0ec0805af79680611fbfbc5d0e825eb18039cf9d
Cr-Commit-Position: refs/heads/master@{#382016}

[enne (OOO), 2016-03-10 00:06:36]

Description was changed from

==========
Allow null begin frame sources in cc::Scheduler

This adds support to make it possible to set the begin frame source in
Scheduler back to null before setting it to something else again.

This is primarily to support the use case of losing an output surface
(which will provide the begin frame source) before asynchronously later
initializing another output surface (with potentially another source).
In this case, there will be some period of time where there is no valid
begin frame source.  The scheduler owner could provide a fake one, but
I think that's more confusing than helpful.

Depends on https://codereview.chromium.org/1774323003
==========

to

==========
Allow null begin frame sources in cc::Scheduler

This adds support to make it possible to set the begin frame source in
Scheduler back to null before setting it to something else again.

This is primarily to support the use case of losing an output surface
(which will provide the begin frame source) before asynchronously later
initializing another output surface (with potentially another source).
In this case, there will be some period of time where there is no valid
begin frame source.  The scheduler owner could provide a fake one, but
I think that's more confusing than helpful.

Depends on https://codereview.chromium.org/1774323003
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel
==========

[enne (OOO), 2016-03-10 00:07:09]

enne@chromium.org changed reviewers:
+ skyostil@chromium.org, sunnyps@chromium.org

[Sami, 2016-03-14 16:12:24]

lgtm.

[enne (OOO), 2016-03-18 17:16:10]

The CQ bit was checked by enne@chromium.org

[commit-bot: I haz the power, 2016-03-18 17:16:42]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1781663004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1781663004/1

[commit-bot: I haz the power, 2016-03-18 18:22:53]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-03-18 18:24:28]

Description was changed from

==========
Allow null begin frame sources in cc::Scheduler

This adds support to make it possible to set the begin frame source in
Scheduler back to null before setting it to something else again.

This is primarily to support the use case of losing an output surface
(which will provide the begin frame source) before asynchronously later
initializing another output surface (with potentially another source).
In this case, there will be some period of time where there is no valid
begin frame source.  The scheduler owner could provide a fake one, but
I think that's more confusing than helpful.

Depends on https://codereview.chromium.org/1774323003
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel
==========

to

==========
Allow null begin frame sources in cc::Scheduler

This adds support to make it possible to set the begin frame source in
Scheduler back to null before setting it to something else again.

This is primarily to support the use case of losing an output surface
(which will provide the begin frame source) before asynchronously later
initializing another output surface (with potentially another source).
In this case, there will be some period of time where there is no valid
begin frame source.  The scheduler owner could provide a fake one, but
I think that's more confusing than helpful.

Depends on https://codereview.chromium.org/1774323003
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Committed: https://crrev.com/0ec0805af79680611fbfbc5d0e825eb18039cf9d
Cr-Commit-Position: refs/heads/master@{#382016}
==========

[commit-bot: I haz the power, 2016-03-18 18:24:29]

Patchset 1 (id:??) landed as
https://crrev.com/0ec0805af79680611fbfbc5d0e825eb18039cf9d
Cr-Commit-Position: refs/heads/master@{#382016}