cc: Clean up max frames/swaps pending usage.

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/logging.h"
@@ skipping 176 matching lines @@
   ProcessScheduledActions();
 }
 
 void Scheduler::SetNeedsPrepareTiles() {
   DCHECK(!IsInsideAction(SchedulerStateMachine::ACTION_PREPARE_TILES));
   state_machine_.SetNeedsPrepareTiles();
   ProcessScheduledActions();
 }
 
 void Scheduler::SetMaxSwapsPending(int max) {
+  // TODO(brianderson): Remove all callers of this function.
+  DCHECK_EQ(1, max) << "Surface and CompositorTimingHistory do not support "
+                       "multiple pending swaps.";
   state_machine_.SetMaxSwapsPending(max);
 }
 
 void Scheduler::DidSwapBuffers() {
   state_machine_.DidSwapBuffers();
 
   // There is no need to call ProcessScheduledActions here because
   // swapping should not trigger any new actions.
   if (!inside_process_scheduled_actions_) {
     DCHECK_EQ(state_machine_.NextAction(), SchedulerStateMachine::ACTION_NONE);
@@ skipping 640 matching lines @@
 }
 
 bool Scheduler::IsBeginMainFrameSentOrStarted() const {
   return (state_machine_.begin_main_frame_state() ==
               SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_SENT ||
           state_machine_.begin_main_frame_state() ==
               SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_STARTED);
 }
 
 }  // namespace cc