DCHECK that scheduler tasks have positive duration.

third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.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 "platform/scheduler/renderer/renderer_scheduler_impl.h"
 
 #include "base/bind.h"
 #include "base/debug/stack_trace.h"
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
@@ skipping 1892 matching lines @@
       MonotonicTimeInSecondsToTimeTicks(start_time);
   GetMainThreadOnly().current_task_start_time = start_time_ticks;
   seqlock_queueing_time_estimator_.seqlock.WriteBegin();
   seqlock_queueing_time_estimator_.data.OnTopLevelTaskStarted(start_time_ticks);
   seqlock_queueing_time_estimator_.seqlock.WriteEnd();
 }
 
 void RendererSchedulerImpl::DidProcessTask(TaskQueue* task_queue,
                                            double start_time,
                                            double end_time) {
+  DCHECK(start_time <= end_time);

[Sami, 2017/06/28 17:42:48]

nit: Consider using DCHECK_LE to get a nicer error message.

[tdresser, 2017/06/28 17:55:02]

Done.

   // TODO(scheduler-dev): Remove conversions when Blink starts using
   // base::TimeTicks instead of doubles for time.
   base::TimeTicks start_time_ticks =
       MonotonicTimeInSecondsToTimeTicks(start_time);
   base::TimeTicks end_time_ticks = MonotonicTimeInSecondsToTimeTicks(end_time);
 
   seqlock_queueing_time_estimator_.seqlock.WriteBegin();
   seqlock_queueing_time_estimator_.data.OnTopLevelTaskCompleted(end_time_ticks);
   seqlock_queueing_time_estimator_.seqlock.WriteEnd();
 
@@ skipping 269 matching lines @@
     case TimeDomainType::VIRTUAL:
       return "virtual";
     default:
       NOTREACHED();
       return nullptr;
   }
 }
 
 }  // namespace scheduler
 }  // namespace blink