cc: Allow sending BeginMainFrame before draw or activation

cc/scheduler/scheduler.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/scheduler/scheduler.h"
 
 #include <algorithm>
 #include "base/auto_reset.h"
 #include "base/debug/trace_event.h"
 #include "base/logging.h"
 #include "cc/debug/devtools_instrumentation.h"
 #include "cc/debug/traced_value.h"
 #include "ui/gfx/frame_time.h"
 
 namespace cc {
 
 Scheduler::Scheduler(SchedulerClient* client,
                      const SchedulerSettings& scheduler_settings,
                      int layer_tree_host_id)
     : settings_(scheduler_settings),
       client_(client),
       layer_tree_host_id_(layer_tree_host_id),
       last_set_needs_begin_impl_frame_(false),
       state_machine_(scheduler_settings),
       inside_process_scheduled_actions_(false),
       inside_action_(SchedulerStateMachine::ACTION_NONE),
       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() {}
 
 void Scheduler::SetCanStart() {
   state_machine_.SetCanStart();
   ProcessScheduledActions();
 }
 
 void Scheduler::SetVisible(bool visible) {
@@ skipping 341 matching lines @@
   // impl thread's deadline.
   base::TimeTicks estimated_draw_time =
       last_begin_impl_frame_args_.frame_time +
       client_->BeginMainFrameToCommitDurationEstimate() +
       client_->CommitToActivateDurationEstimate();
 
   return estimated_draw_time < last_begin_impl_frame_args_.deadline;
 }
 
 }  // namespace cc