Avoid DCHECK in ExternalBeginFrameSource::GetMissedBeginFrameArgs caused by out of order frame time

cc/scheduler/begin_frame_source.cc

 // Copyright 2014 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/begin_frame_source.h"
 
 #include <stddef.h>
 
 #include "base/atomic_sequence_num.h"
 #include "base/auto_reset.h"
@@ skipping 319 matching lines @@
   }
 }
 
 BeginFrameArgs ExternalBeginFrameSource::GetMissedBeginFrameArgs(
     BeginFrameObserver* obs) {
   if (!last_begin_frame_args_.IsValid())
     return BeginFrameArgs();
 
   const BeginFrameArgs& last_args = obs->LastUsedBeginFrameArgs();
   if (last_args.IsValid() &&
-      last_begin_frame_args_.frame_time == last_args.frame_time) {
+      last_begin_frame_args_.frame_time <= last_args.frame_time) {
     return BeginFrameArgs();
   }
 
   DCHECK((last_begin_frame_args_.source_id != last_args.source_id) ||
          (last_begin_frame_args_.sequence_number > last_args.sequence_number))
       << "current " << last_begin_frame_args_.AsValue()->ToString() << ", last "
       << last_args.AsValue()->ToString();
   BeginFrameArgs missed_args = last_begin_frame_args_;
   missed_args.type = BeginFrameArgs::MISSED;
   return missed_args;
 }
 
 }  // namespace cc