Use vsync manager regardless of begin frame settings

ui/compositor/compositor.cc

Index: ui/compositor/compositor.cc
diff --git a/ui/compositor/compositor.cc b/ui/compositor/compositor.cc
index 7e7b109a09d10ec2ed88bd14313d2cc37cf5c9d4..27b52437bd20c54ae9e7e5b3e6e3addacc7ebcaf 100644
--- a/ui/compositor/compositor.cc
+++ b/ui/compositor/compositor.cc
@@ -398,10 +398,13 @@ bool Compositor::GetScrollOffsetForLayer(int layer_id,
 void Compositor::SetAuthoritativeVSyncInterval(
     const base::TimeDelta& interval) {
   context_factory_->SetAuthoritativeVSyncInterval(this, interval);
-  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
-         cc::switches::kDisableBeginFrameScheduling)) {
-    vsync_manager_->SetAuthoritativeVSyncInterval(interval);
-  }
+  vsync_manager_->SetAuthoritativeVSyncInterval(interval);
+}
+
+void Compositor::SetDisplayVSyncParameters(base::TimeTicks timebase,
+                                           base::TimeDelta interval) {

[piman, 2016/08/24 21:23:58]

This is only called on mac, by BrowserCompositorMac::UpdateVSyncParameters,
right?
In particular, BrowserCompositorOutputSurface skips it and goes directly to the
BeginFrameSource and the VSyncManager.

There doesn't seem like there's a good way to make it more consistent, but it
would be nice to document this fact.

[enne (OOO), 2016/08/24 21:48:37]

Do you want more than the comment I added in compositor.h?

And yeah, I felt sad about adding this at the time, but I couldn't come up with
a better way to route this.  This isn't a great alternate route, but it's not
that terrible either.  One possibility is that I could go Compositor ->
GpuProcessTransportFactory -> Display -> BrowserCompositorOutputSurface if I
made Display use BrowserCompositorOutputSurface instead of just plain
OutputSurface, but I'm not sure if I like Display knowing that.

+  context_factory_->SetDisplayVSyncParameters(this, timebase, interval);
+  vsync_manager_->UpdateVSyncParameters(timebase, interval);
 }
 
 void Compositor::SetAcceleratedWidget(gfx::AcceleratedWidget widget) {