Allow Windows to use system Vsync if only one window is swapping

Allow Windows to use system Vsync if only one window is swapping

This makes the common case (single browser window) smoother. Having
multiple swapping windows visible will force the previous behavior.

This patch differs from a previous variant (https://codereview.chromium.org/708483003)
in that there's now a "timeout" before we attempt turning on vsync again.
Specifically, we need to go for 60 frames without a frame where two
surfaces swap in order to turn Vsync on. This accounts for cases where
low-frequency updates in one window (blinking cursor) don't trigger
frequent vsync state changes. Also prevents pathologically bad cases
where two frequently updating windows would cause one another to skip
alternating frames.

BUG=422000
Committed: https://crrev.com/9b71e13d22829c2df1620211049a6032628ebea8
Cr-Commit-Position: refs/heads/master@{#309861}

[bajones, 2014-11-20 18:06:55]

bajones@chromium.org changed reviewers:
+ brianderson@chromium.org, jbauman@chromium.org, kbr@chromium.org

[bajones, 2014-11-20 18:06:56]

PTAL at this new variant of the Vsync fix. I feel like the 60-frame threshold
allows the behavior to be much more predictable than the previous version. I
still suspect that this will cause latency regressions on the perf bots, but
Brian has said he's comfortable with that in order to increase smoothness, and
that the latency can be examined separately.

[Ken Russell (switch to Gerrit), 2014-11-21 00:05:58]

LGTM overall, once it compiles on all platforms. It does break some abstraction
barriers. A couple of comments.

https://codereview.chromium.org/749483002/diff/1/ui/gl/gl_surface.h
File ui/gl/gl_surface.h (right):

https://codereview.chromium.org/749483002/diff/1/ui/gl/gl_surface.h#newcode137
ui/gl/gl_surface.h:137: virtual void SetSwapInterval(int interval);
Please document this, especially since it doesn't really do the SetSwapInterval
call, and SetSwapInterval is a context-level API, not a surface-level API.

https://codereview.chromium.org/749483002/diff/1/ui/gl/gl_surface_egl.cc
File ui/gl/gl_surface_egl.cc (right):

https://codereview.chromium.org/749483002/diff/1/ui/gl/gl_surface_egl.cc#newc...
ui/gl/gl_surface_egl.cc:489: eglSwapInterval(GetDisplay(), 0);
eglSwapInterval applies to the current context. There seems to be an implicit
assumption here that there's only one context ever bound to a given surface.
Should make that explicit with a comment.

[bajones, 2015-01-02 20:55:51]

The CQ bit was checked by bajones@chromium.org

[commit-bot: I haz the power, 2015-01-02 20:56:53]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/749483002/40001

[commit-bot: I haz the power, 2015-01-02 21:17:08]

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

[commit-bot: I haz the power, 2015-01-02 21:17:09]

Try jobs failed on following builders:
  linux_gpu on tryserver.chromium.gpu
(http://build.chromium.org/p/tryserver.chromium.gpu/builders/linux_gpu/builds/...)

[bajones, 2015-01-02 22:08:09]

The CQ bit was checked by bajones@chromium.org

[commit-bot: I haz the power, 2015-01-02 22:09:17]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/749483002/60001

[commit-bot: I haz the power, 2015-01-02 23:38:08]

Committed patchset #4 (id:60001)

[commit-bot: I haz the power, 2015-01-02 23:38:55]

Patchset 4 (id:??) landed as
https://crrev.com/9b71e13d22829c2df1620211049a6032628ebea8
Cr-Commit-Position: refs/heads/master@{#309861}

[jdduke (slow), 2015-01-08 01:20:32]

On 2015/01/02 23:38:55, I haz the power (commit-bot) wrote:
> Patchset 4 (id:??) landed as
> https://crrev.com/9b71e13d22829c2df1620211049a6032628ebea8
> Cr-Commit-Position: refs/heads/master@{#309861}

I'm guessing this accounts for the (relatively) substantial input latency
improvements on Windows?

https://chromeperf.appspot.com/report?masters=ChromiumPerf&bots=chromium-rel-...

https://chromeperf.appspot.com/report?masters=ChromiumPerf&bots=chromium-rel-...