cc: Add SwapPromiseManager and SurfaceSequenceGenerator.

cc/trees/layer_tree.h

Index: cc/trees/layer_tree.h
diff --git a/cc/trees/layer_tree.h b/cc/trees/layer_tree.h
index 77d105c84d16bc81af816756b5673297f4be8db1..19f5ec8d58d1d6aed2323138adebc06940fc40a0 100644
--- a/cc/trees/layer_tree.h
+++ b/cc/trees/layer_tree.h
@@ -40,6 +40,8 @@ class LayerTreeImpl;
 class LayerTreeSettings;
 struct PendingPageScaleAnimation;
 class UIResourceManager;
+class SwapPromiseManager;
+class SurfaceSequenceGenerator;
 
 class CC_EXPORT LayerTree : public MutatorHostClient {
  public:
@@ -124,6 +126,8 @@ class CC_EXPORT LayerTree : public MutatorHostClient {
 
   UIResourceManager* GetUIResourceManager() const;
   const LayerTreeSettings& GetSettings() const;
+  SwapPromiseManager* GetSwapPromiseManager() const;
+  SurfaceSequenceGenerator* GetSurfaceSequenceGenerator() const;
 
   // Methods which should only be used internally in cc ------------------
   void RegisterLayer(Layer* layer);