Force use of and cache render surface.

ui/compositor/layer.h

Index: ui/compositor/layer.h
diff --git a/ui/compositor/layer.h b/ui/compositor/layer.h
index 89602807c8cfc58626b3b81f10f9e7de684fc8e4..0bd2faedf395a46e523719cc1b1909d022202749 100644
--- a/ui/compositor/layer.h
+++ b/ui/compositor/layer.h
@@ -405,6 +405,12 @@ class COMPOSITOR_EXPORT Layer
     return frame_size_in_dip_;
   }
 
+  // Force use of render surface. Note that this also disables
+  // occlusion culling in favor of efficient caching. This should
+  // only be used when paying the cost of creating a render
+  // surface even if layer is invisible is not a problem.
+  void SetForceRenderSurface(bool force);

[danakj, 2017/05/09 14:56:54]

This seems like something the Layer should set when it is animating, not
something the client should set permanently. wdyt?

[reveman, 2017/05/09 15:49:25]

The main use-case is to enable this when animating but I think we also want
manual control. The new background blur UI that is being worked on is one case
where I think we want to use this without animating to improve performance. If
we want to start with just for animations then that's fine with me.

[danakj, 2017/05/09 15:51:51]

Background filters are implemented via a separate render pass, so I'd expect
that to implicitly get one or the feature wouldn't work. I'd prefer it tied to
animations until we have a more clear picture how that'd work, and maybe that
can be tied to the feature instead of a bit that might be set an inappropriate
times, which would only hurt performance.

[reveman, 2017/05/10 13:06:17]

Animations for now sounds good. There might be some animations where we want to
avoid this though (e.g.transform only) so some control for outside ui::Layer
might still be needed.

[wutao, 2017/05/11 19:36:35]

Acknowledged.

+
  private:
   friend class LayerOwner;
   class LayerMirror;