cc: Allow sending BeginMainFrame before draw or activation

cc/scheduler/scheduler.cc

Index: cc/scheduler/scheduler.cc
diff --git a/cc/scheduler/scheduler.cc b/cc/scheduler/scheduler.cc
index 84852fa9adbf3316e78b43a578987324937b6d02..2e6b2a809ded4ec213136c537bc7bb6f1228bd4e 100644
--- a/cc/scheduler/scheduler.cc
+++ b/cc/scheduler/scheduler.cc
@@ -27,6 +27,9 @@ Scheduler::Scheduler(SchedulerClient* client,
       weak_factory_(this) {
   DCHECK(client_);
   DCHECK(!state_machine_.BeginImplFrameNeeded());
+  if (settings_.start_commit_before_activate_enabled) {
+    DCHECK(settings_.start_commit_before_draw_enabled);
+  }
 }
 
 Scheduler::~Scheduler() {}