DCHECK that scheduler tasks have positive duration.

third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.cc

Index: third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.cc
diff --git a/third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.cc b/third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.cc
index 542a75f0f51009d909010fb0839e825128e84e05..a336ee2243200213e2797a5dffc95b91892bd47f 100644
--- a/third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.cc
+++ b/third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.cc
@@ -1910,6 +1910,7 @@ void RendererSchedulerImpl::WillProcessTask(TaskQueue* task_queue,
 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 =