Use GLX_SGI_video_sync to get a vblank signal.

content/common/gpu/image_transport_surface.cc

Index: content/common/gpu/image_transport_surface.cc
diff --git a/content/common/gpu/image_transport_surface.cc b/content/common/gpu/image_transport_surface.cc
index e0f1e2f0e68c665b7ef6e508e348fd3cdb66bd0b..d0241e967926b00e8d5921575c11ffa131d2a661 100644
--- a/content/common/gpu/image_transport_surface.cc
+++ b/content/common/gpu/image_transport_surface.cc
@@ -353,11 +353,9 @@ gfx::Size PassThroughImageTransportSurface::GetSize() {
 PassThroughImageTransportSurface::~PassThroughImageTransportSurface() {}
 
 void PassThroughImageTransportSurface::SendVSyncUpdateIfAvailable() {
-  base::TimeTicks timebase;
-  base::TimeDelta interval;
-  if (GetVSyncParameters(&timebase, &interval)) {
-    helper_->SendUpdateVSyncParameters(timebase, interval);
-  }
+  GetVSyncParameters(
+      base::Bind(&ImageTransportHelper::SendUpdateVSyncParameters,
+                 base::Unretained(helper_.get())));

[piman, 2012/11/08 23:51:16]

What guarantees that the helper is still valid when the callback is called?

[jonathan.backer, 2012/11/09 17:02:35]

PTITSurface owns ITHelper and GLSurfaceGLX
GLSurfaceGLX owns VsyncProvider

The callback will only be called be called while VsyncProvider is in scope.

I can make this more transparent by having the ITHelper vend a WeakPtr. Your
call.

[piman, 2012/11/09 18:08:05]

Since GLSurfaceGLX is refcounted, it's hard to guarantee (forever) it won't
outlive the helper. If we believe it's true today, and we can assert this, we
should do that, otherwise a WeakPtr is fine.

 }
 
 }  // namespace content