Add SwapPromise support to LayerTreeHost and LayerTreeImpl

cc/trees/layer_tree_host.h

Index: cc/trees/layer_tree_host.h
diff --git a/cc/trees/layer_tree_host.h b/cc/trees/layer_tree_host.h
index 54962fc4eafdf401556a0450315b90b4f8e183a0..47bfa115d449a8c6846edf4e4a1461cb6cbd451b 100644
--- a/cc/trees/layer_tree_host.h
+++ b/cc/trees/layer_tree_host.h
@@ -21,6 +21,7 @@
 #include "cc/animation/animation_events.h"
 #include "cc/base/cc_export.h"
 #include "cc/base/scoped_ptr_vector.h"
+#include "cc/base/swap_promise.h"
 #include "cc/debug/micro_benchmark.h"
 #include "cc/debug/micro_benchmark_controller.h"
 #include "cc/input/input_handler.h"
@@ -286,6 +287,12 @@ class CC_EXPORT LayerTreeHost {
                               scoped_ptr<base::Value> value,
                               const MicroBenchmark::DoneCallback& callback);
 
+  // Call this function when you expect there to be a swap buffer.
+  // See swap_promise.h for how to use SwapPromise.
+  void QueueSwapPromise(scoped_ptr<SwapPromise> swap_promise);
+
+  void BreakSwapPromises(SwapPromise::DidNotSwapReason reason);
+
  protected:
   LayerTreeHost(LayerTreeHostClient* client,
                 SharedBitmapManager* manager,
@@ -433,6 +440,8 @@ class CC_EXPORT LayerTreeHost {
 
   SharedBitmapManager* shared_bitmap_manager_;
 
+  ScopedPtrVector<SwapPromise> swap_promise_list_;
+
   DISALLOW_COPY_AND_ASSIGN(LayerTreeHost);
 };