Make sure scheduler shutdown prevents idle tasks from running

third_party/WebKit/Source/platform/scheduler/child/idle_helper.cc

Index: third_party/WebKit/Source/platform/scheduler/child/idle_helper.cc
diff --git a/third_party/WebKit/Source/platform/scheduler/child/idle_helper.cc b/third_party/WebKit/Source/platform/scheduler/child/idle_helper.cc
index 3daea10ee1023dbc7a3bace837268058ab185e54..d9a946e874448d73630a128a18852d6d463418c6 100644
--- a/third_party/WebKit/Source/platform/scheduler/child/idle_helper.cc
+++ b/third_party/WebKit/Source/platform/scheduler/child/idle_helper.cc
@@ -36,6 +36,7 @@ IdleHelper::IdleHelper(
           required_quiescence_duration_before_long_idle_period),
       disabled_by_default_tracing_category_(
           disabled_by_default_tracing_category),
+      is_shutdown_(false),
       weak_factory_(this) {
   weak_idle_helper_ptr_ = weak_factory_.GetWeakPtr();
   enable_next_long_idle_period_closure_.Reset(
@@ -53,6 +54,18 @@ IdleHelper::IdleHelper(
 }
 
 IdleHelper::~IdleHelper() {
+  Shutdown();
+}
+
+void IdleHelper::Shutdown() {
+  if (is_shutdown_)
+    return;
+
+  EndIdlePeriod();
+  is_shutdown_ = true;
+  weak_factory_.InvalidateWeakPtrs();
+  // Belt & braces, might not be needed.
+  idle_queue_->SetQueueEnabled(false);
   helper_->RemoveTaskObserver(this);
 }
 
@@ -109,9 +122,6 @@ IdleHelper::IdlePeriodState IdleHelper::ComputeNewLongIdlePeriodState(
 bool IdleHelper::ShouldWaitForQuiescence() {
   helper_->CheckOnValidThread();
 
-  if (helper_->IsShutdown())
-    return false;
-
   if (required_quiescence_duration_before_long_idle_period_ ==
       base::TimeDelta()) {
     return false;
@@ -126,7 +136,7 @@ bool IdleHelper::ShouldWaitForQuiescence() {
 void IdleHelper::EnableLongIdlePeriod() {
   TRACE_EVENT0(disabled_by_default_tracing_category_, "EnableLongIdlePeriod");
   helper_->CheckOnValidThread();
-  if (helper_->IsShutdown())
+  if (is_shutdown_)
     return;
 
   // End any previous idle period.
@@ -158,6 +168,7 @@ void IdleHelper::EnableLongIdlePeriod() {
 void IdleHelper::StartIdlePeriod(IdlePeriodState new_state,
                                  base::TimeTicks now,
                                  base::TimeTicks idle_period_deadline) {
+  DCHECK(!is_shutdown_);
   DCHECK_GT(idle_period_deadline, now);
   helper_->CheckOnValidThread();
   DCHECK(IsInIdlePeriod(new_state));
@@ -182,6 +193,9 @@ void IdleHelper::StartIdlePeriod(IdlePeriodState new_state,
 }
 
 void IdleHelper::EndIdlePeriod() {
+  if (is_shutdown_)
+    return;
+
   helper_->CheckOnValidThread();
   TRACE_EVENT0(disabled_by_default_tracing_category_, "EndIdlePeriod");
 
@@ -197,10 +211,13 @@ void IdleHelper::EndIdlePeriod() {
                      base::TimeTicks());
 }
 
-void IdleHelper::WillProcessTask(const base::PendingTask& pending_task) {}
+void IdleHelper::WillProcessTask(const base::PendingTask& pending_task) {
+  DCHECK(!is_shutdown_);
+}
 
 void IdleHelper::DidProcessTask(const base::PendingTask& pending_task) {
   helper_->CheckOnValidThread();
+  DCHECK(!is_shutdown_);
   TRACE_EVENT0(disabled_by_default_tracing_category_, "DidProcessTask");
   if (IsInIdlePeriod(state_.idle_period_state()) &&
       state_.idle_period_state() !=
@@ -221,6 +238,7 @@ void IdleHelper::DidProcessTask(const base::PendingTask& pending_task) {
 
 void IdleHelper::UpdateLongIdlePeriodStateAfterIdleTask() {
   helper_->CheckOnValidThread();
+  DCHECK(!is_shutdown_);
   DCHECK(IsInLongIdlePeriod(state_.idle_period_state()));
   TRACE_EVENT0(disabled_by_default_tracing_category_,
                "UpdateLongIdlePeriodStateAfterIdleTask");
@@ -262,6 +280,8 @@ base::TimeTicks IdleHelper::CurrentIdleTaskDeadline() const {
 
 void IdleHelper::OnIdleTaskPosted() {
   TRACE_EVENT0(disabled_by_default_tracing_category_, "OnIdleTaskPosted");
+  if (is_shutdown_)
+    return;
   if (idle_task_runner_->RunsTasksOnCurrentThread()) {
     OnIdleTaskPostedOnMainThread();
   } else {
@@ -273,6 +293,8 @@ void IdleHelper::OnIdleTaskPosted() {
 void IdleHelper::OnIdleTaskPostedOnMainThread() {
   TRACE_EVENT0(disabled_by_default_tracing_category_,
                "OnIdleTaskPostedOnMainThread");
+  if (is_shutdown_)
+    return;
   if (state_.idle_period_state() ==
       IdlePeriodState::IN_LONG_IDLE_PERIOD_PAUSED) {
     // Restart long idle period ticks.
@@ -283,12 +305,15 @@ void IdleHelper::OnIdleTaskPostedOnMainThread() {
 
 base::TimeTicks IdleHelper::WillProcessIdleTask() {
   helper_->CheckOnValidThread();
+  DCHECK(!is_shutdown_);
   state_.TraceIdleIdleTaskStart();
   return CurrentIdleTaskDeadline();
 }
 
 void IdleHelper::DidProcessIdleTask() {
   helper_->CheckOnValidThread();
+  if (is_shutdown_)
+    return;
   state_.TraceIdleIdleTaskEnd();
   if (IsInLongIdlePeriod(state_.idle_period_state())) {
     UpdateLongIdlePeriodStateAfterIdleTask();