[cc] Set BeginFrame sequence numbers on CompositorFrames from Scheduler.

cc/scheduler/scheduler_state_machine.h

Index: cc/scheduler/scheduler_state_machine.h
diff --git a/cc/scheduler/scheduler_state_machine.h b/cc/scheduler/scheduler_state_machine.h
index 2ad99993d683fa73be950a2eab41b1937fbdc4dd..5f24386dd08a153bd60c28986d0879b3695a4521 100644
--- a/cc/scheduler/scheduler_state_machine.h
+++ b/cc/scheduler/scheduler_state_machine.h
@@ -290,6 +290,9 @@ class CC_EXPORT SchedulerStateMachine {
   }
 
   uint32_t begin_frame_source_id() const { return begin_frame_source_id_; }
+  uint64_t last_begin_frame_sequence_number_active_tree_was_fresh() const {
+    return last_begin_frame_sequence_number_active_tree_was_fresh_;
+  }
   uint64_t last_begin_frame_sequence_number_compositor_frame_was_fresh() const {
     return last_begin_frame_sequence_number_compositor_frame_was_fresh_;
   }