scheduler: Fix debug build crash with --disable-blink-scheduler

content/renderer/scheduler/single_thread_idle_task_runner.cc

Index: content/renderer/scheduler/single_thread_idle_task_runner.cc
diff --git a/content/renderer/scheduler/single_thread_idle_task_runner.cc b/content/renderer/scheduler/single_thread_idle_task_runner.cc
index b6eb5ce9c64079a9b601e9c0f1467c164c63341c..cb3db7de530a1777b938bcaacaa7a9e046aadb43 100644
--- a/content/renderer/scheduler/single_thread_idle_task_runner.cc
+++ b/content/renderer/scheduler/single_thread_idle_task_runner.cc
@@ -16,8 +16,10 @@ SingleThreadIdleTaskRunner::SingleThreadIdleTaskRunner(
     : idle_priority_task_runner_(idle_priority_task_runner),
       after_wakeup_task_runner_(after_wakeup_task_runner),
       deadline_supplier_(deadline_supplier) {
-  DCHECK(idle_priority_task_runner_->RunsTasksOnCurrentThread());
-  DCHECK(after_wakeup_task_runner_->RunsTasksOnCurrentThread());
+  DCHECK(!idle_priority_task_runner_ ||
+         idle_priority_task_runner_->RunsTasksOnCurrentThread());
+  DCHECK(!after_wakeup_task_runner_ ||
+         after_wakeup_task_runner_->RunsTasksOnCurrentThread());
 }
 
 SingleThreadIdleTaskRunner::~SingleThreadIdleTaskRunner() {