SF: Move TransactionStart from VsyncModulator to Scheduler

This is part of go/surface-flinger-scheduler.

Test: SF tests pass.
Change-Id: I45872aeb67603e15f1d5080d0b9440bc986579e4
diff --git a/services/surfaceflinger/Scheduler/Scheduler.h b/services/surfaceflinger/Scheduler/Scheduler.h
index fcb46e6..d7c9651 100644
--- a/services/surfaceflinger/Scheduler/Scheduler.h
+++ b/services/surfaceflinger/Scheduler/Scheduler.h
@@ -29,6 +29,9 @@
 
 class Scheduler {
 public:
+    // Enum to indicate whether to start the transaction early, or at vsync time.
+    enum class TransactionStart { EARLY, NORMAL };
+
     /* The scheduler handle is a BBinder object passed to the client from which we can extract
      * an ID for subsequent operations.
      */