chromeos: power: Make RendererFreezer asynchronous

chromeos: power: Make RendererFreezer asynchronous

In preparation for the upcoming integration with service workers, which
need to do a lot of asynchronous work before the renderers are frozen,
have the RendererFreezer grab a suspend readiness callback that it will
run at some point in the future when it is ready to suspend.

BUG=364339, 411046
Signed-off-by: Chirantan Ekbote <chirantan@chromium.org>;

Committed: https://crrev.com/d0f2d2367d60389c4b296d823b19bc34df8e769f
Cr-Commit-Position: refs/heads/master@{#293426}

[Chirantan Ekbote, 2014-09-04 20:29:23]

chirantan@chromium.org changed reviewers:
+ derat@chromium.org

[Chirantan Ekbote, 2014-09-04 22:24:07]

Please take a look.

[Daniel Erat, 2014-09-04 22:38:45]

lgtm

(it'd be nice to have tests for this code, though)

[Chirantan Ekbote, 2014-09-05 00:14:05]

The CQ bit was checked by chirantan@chromium.org

[Chirantan Ekbote, 2014-09-05 00:14:06]

Ok, I'll refactor and add tests in a separate CL.

[commit-bot: I haz the power, 2014-09-05 00:16:40]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/chirantan@chromium.org/536753004/20001

[commit-bot: I haz the power, 2014-09-05 03:51:02]

Committed patchset #2 (id:20001) as 7c157c765d047af9279a76054281ff1a0df6bb5b

[commit-bot: I haz the power, 2014-09-10 03:36:25]

Patchset 2 (id:??) landed as
https://crrev.com/d0f2d2367d60389c4b296d823b19bc34df8e769f
Cr-Commit-Position: refs/heads/master@{#293426}