cc: Add SwapPromiseManager and SurfaceSequenceGenerator.

cc/BUILD.gn

Index: cc/BUILD.gn
diff --git a/cc/BUILD.gn b/cc/BUILD.gn
index c8acb819daa6c16bf4a0b6e93d31e9455a4eaef5..b4dcd57f26d7c0c5ea710585904c4f558748af89 100644
--- a/cc/BUILD.gn
+++ b/cc/BUILD.gn
@@ -538,6 +538,10 @@ component("cc") {
     "trees/scroll_node.h",
     "trees/single_thread_proxy.cc",
     "trees/single_thread_proxy.h",
+    "trees/surface_sequence_generator.cc",
+    "trees/surface_sequence_generator.h",
+    "trees/swap_promise_manager.cc",
+    "trees/swap_promise_manager.h",
     "trees/swap_promise_monitor.cc",
     "trees/swap_promise_monitor.h",
     "trees/task_runner_provider.cc",
@@ -938,6 +942,8 @@ test("cc_unittests") {
     "trees/occlusion_unittest.cc",
     "trees/property_tree_unittest.cc",
     "trees/proxy_common_unittest.cc",
+    "trees/surface_sequence_generator_unittest.cc",
+    "trees/swap_promise_manager_unittest.cc",
     "trees/tree_synchronizer_unittest.cc",
 
     # Surfaces test files.