cc: Add SwapPromiseManager and SurfaceSequenceGenerator.

cc/layers/layer.h

Index: cc/layers/layer.h
diff --git a/cc/layers/layer.h b/cc/layers/layer.h
index 72399af2f0a5a8547815898d36105463d32947db..30e9ed447c6a66e7e876dec9ca868143159d0feb 100644
--- a/cc/layers/layer.h
+++ b/cc/layers/layer.h
@@ -391,8 +391,6 @@ class CC_EXPORT Layer : public base::RefCounted<Layer> {
   // of |proto| is only read if |needs_push_properties_| is set.
   void FromLayerPropertiesProto(const proto::LayerProperties& proto);
 
-  // TODO(xingliu): Layer will hold LayerTree instead of LayerTreeHost.
-  // http://crbug.com/628683

[Khushal, 2016/09/13 17:31:11]

When I actually got around to having Layers go through the tree to use the host,
it was adding an unnecessary layer of wrapping, since Layers use everything from
the host anyway. https://codereview.chromium.org/2331983002/ will change it to a
protected member but I think we can leave everything as-is for Layer and
friends.
vmpstr@, could you take another look?

   LayerTreeHost* layer_tree_host() { return layer_tree_host_; }
   const LayerTreeHost* layer_tree_host() const { return layer_tree_host_; }
   LayerTree* GetLayerTree() const;